SmogRank / Episodes / United States

Eastern United States and Canada, 25 June to 2 July 2023

For 8 days, from 25 June to 2 July 2023, 280 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Saguenay, Quebec, Canada: 453.0 µg/m³ on 25 June, about 48× its usual 9.4.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached280in 2 countries
Days825 June to 2 July 2023
Worst day29 June208 cities counted
Furthest above usual53×North Bay

Day by day

29 June 208 cities at twice their usual or more
WheelingCharlestonAthensClarksvilleConwayColumbiaMcDonoughHuntsvillePaducahDecaturSavannahJacksonDyersburgAlbanyMontgomeryBartlettWest MemphisDerryLaconiaHaverhillPortsmouthJacksonHattiesburgLewistonLittle RockSpringfieldLibertyRaymoreKansas CityKansas CitySpringdaleSaint JosephOlatheBangorFort SmithTopekaTexarkanaBellevueOmahaShreveportTulsaJenksLincolnMcAlesterPonca CityDerbyWichitaFrederictonAdaSaint JohnEdmondOklahoma CityMooreGrand IslandDallasCorsicanaDentonMiramichiSaginawFort WorthLawtonDartmouthCharlottetownGadsdenBirminghamPortlandSaint AndrewsHernandoSpartanburgPhenix CityClaytonNorth CharlestonMaconWarner RobinsAugustaFlorenceFayettevilleLynnGreenvilleAtlantaHendersonvillePatersonChesapeakeCandler-McAfeeLowellCharlotteWatertownAshevilleGreenvilleBostonBrookingsHueytownHickoryPleasantvilleLawrencevilleGainesvilleEast RidgeWest FargoCookevilleAberdeenTrussvilleRoanoke RapidsQuincyLexingtonDurhamNew LondonMorrisvilleCheektowagaSioux FallsBrocktonToms RiverMaryvilleHartfordCoventryRaleighGreensboroMonctonKingsportHempsteadDanburyChattanoogaKnoxvilleJersey CityEast HamptonClemmonsAlbanyHolbrookSuperiorElizabethProvidenceFall RiverArnoldNew York CityEwingNew HavenBurlingtonFort LeeLindenWaterburyKeeneEdmundstonSpringfieldSouth VinelandWinston-SalemTrentonValley StationGranite CitySt. LouisPennsaukenPhiladelphiaElizabethtownBridgeportSaint PaulEast Saint LouisTorontoDuluthHopewellWhite PlainsNorth ChicopeePittsfieldBlaineKitchenerRutlandMinneapolisPawtucketWorcesterNew BrunswickDoverBensalemLondonUniversity CityShakopeeRoanokeRichmondBrantfordWashingtonLemayAshlandOwensboroScaggsvilleSaint MichaelApple ValleyBurnsvilleHamiltonLouisvilleSaint CloudNorristownOak LawnBuffaloBayonneGreenfieldBarrieDes MoinesJeffersontownAllentownSaint MatthewsLebanonNew CityRochesterNorwoodEau ClaireNew AlbanyCharlottesvilleNewarkChicagoRockvilleAnkenySt. ThomasGaryMiddletownHarrisburgKingstonLa CrosseKenmoreScrantonEvansvilleLimaReadingCincinnatiLexington-FayetteEdgewoodSpringfieldPortageFishersBethlehemLancasterToledoHunt ValleyChesterQuébecYorkSouth LaurelWest MifflinL'Ancienne-LorettePeterboroughWilmingtonJeffersonvilleRedfordBearFlintRose HillUticaElktonFranklin ParkCarlisleRochesterBaltimoreSpringfieldDaytonElkhartMasonHollandSyracuseGreen BayCornwallPainesvilleWhite OakLebanonWaterlooBay CityMcKeesportNewburghState CollegeLansingErieSarniaHammondTrois-RivièresSteubenvilleSt. CatharinesAndersonFort ThomasGahannaJohnstownDetroitAppletonTerre HauteHagerstownDearbornClevelandWarrenLafayettePort HuronCalumet CityWindsorGranbyMontréalPittsburghKokomoEast ChicagoBellevilleGrand RapidsAltoonaKalamazooDorvalIndianapolisDublinNorthbrookColumbusNapervilleHermitageBrossardSouth BendDes PlainesLincoln ParkSaint-Jean-sur-RichelieuWeirton HeightsIowa CityTaylorYpsilantiCaryWilkinsburgYoungstownDrummondvilleSpringfieldChathamShaker HeightsJenisonJolietDavenportRivière-des-Prairies–Pointe-aux-TremblesMilwaukeeBloomingtonMolineZionCantonSault Ste. MarieClintonOttawaRockfordMuscatineAkronShawiniganDecaturSouth MilwaukeeWaukeshaMedinaMadisonBloomingtonGreater SudburyRouyn-NorandaSaguenayNorth Bay
22 Jun23242526272829301 Jul2345
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

SaguenaySaguenay, 22 June: 27.4 µg/m³Saguenay, 23 June: 34.9 µg/m³Saguenay, 24 June: 139.0 µg/m³Saguenay, 25 June: 453.0 µg/m³, 48× its usual 9.4Saguenay, 26 June: 78.0 µg/m³, 8.7× its usual 9.0Saguenay, 27 June: 11.8 µg/m³Saguenay, 28 June: 8.9 µg/m³Saguenay, 29 June: 8.2 µg/m³Saguenay, 30 June: 11.2 µg/m³Saguenay, 1 July: 16.6 µg/m³Saguenay, 2 July: 18.4 µg/m³Saguenay, 3 July: 14.7 µg/m³Saguenay, 4 July: 16.1 µg/m³Saguenay, 5 July: 17.2 µg/m³North BayNorth Bay, 22 June: 34.3 µg/m³North Bay, 23 June: 13.1 µg/m³North Bay, 24 June: 37.2 µg/m³North Bay, 25 June: 397.0 µg/m³, 53× its usual 7.5North Bay, 26 June: 139.0 µg/m³, 19× its usual 7.4North Bay, 27 June: 43.7 µg/m³, 6.2× its usual 7.1North Bay, 28 June: 52.5 µg/m³, 7.6× its usual 6.9North Bay, 29 June: 20.4 µg/m³North Bay, 30 June: 41.0 µg/m³, 6.0× its usual 6.8North Bay, 1 July: 36.9 µg/m³, 5.6× its usual 6.6North Bay, 2 July: 15.5 µg/m³North Bay, 3 July: 11.6 µg/m³North Bay, 4 July: 13.3 µg/m³North Bay, 5 July: 11.5 µg/m³Rouyn-NorandaRouyn-Noranda, 22 June: 51.9 µg/m³Rouyn-Noranda, 23 June: 45.6 µg/m³Rouyn-Noranda, 24 June: 87.0 µg/m³Rouyn-Noranda, 25 June: 221.0 µg/m³, 28× its usual 7.8Rouyn-Noranda, 26 June: 312.0 µg/m³, 41× its usual 7.6Rouyn-Noranda, 27 June: 219.0 µg/m³, 29× its usual 7.6Rouyn-Noranda, 28 June: 16.9 µg/m³Rouyn-Noranda, 29 June: no readingRouyn-Noranda, 30 June: 26.4 µg/m³, 3.5× its usual 7.6Rouyn-Noranda, 1 July: 15.6 µg/m³Rouyn-Noranda, 2 July: 14.6 µg/m³Rouyn-Noranda, 3 July: 19.6 µg/m³Rouyn-Noranda, 4 July: 19.5 µg/m³Rouyn-Noranda, 5 July: 12.8 µg/m³Greater SudburyGreater Sudbury, 22 June: 46.0 µg/m³Greater Sudbury, 23 June: 21.0 µg/m³Greater Sudbury, 24 June: 58.5 µg/m³Greater Sudbury, 25 June: 275.0 µg/m³, 34× its usual 8.0Greater Sudbury, 26 June: 88.1 µg/m³, 11× its usual 7.9Greater Sudbury, 27 June: 121.0 µg/m³, 16× its usual 7.7Greater Sudbury, 28 June: 4.0 µg/m³Greater Sudbury, 29 June: 11.4 µg/m³Greater Sudbury, 30 June: 44.9 µg/m³, 6.0× its usual 7.5Greater Sudbury, 1 July: 24.5 µg/m³Greater Sudbury, 2 July: 13.5 µg/m³Greater Sudbury, 3 July: 13.7 µg/m³Greater Sudbury, 4 July: 14.3 µg/m³Greater Sudbury, 5 July: 12.8 µg/m³ShawiniganShawinigan, 22 June: 6.7 µg/m³Shawinigan, 23 June: 7.7 µg/m³Shawinigan, 24 June: 12.5 µg/m³Shawinigan, 25 June: 192.0 µg/m³, 23× its usual 8.3Shawinigan, 26 June: 49.4 µg/m³, 6.0× its usual 8.3Shawinigan, 27 June: 4.7 µg/m³Shawinigan, 28 June: 6.6 µg/m³Shawinigan, 29 June: 7.1 µg/m³Shawinigan, 30 June: 27.2 µg/m³, 3.4× its usual 8.0Shawinigan, 1 July: 33.3 µg/m³, 4.3× its usual 7.8Shawinigan, 2 July: 25.6 µg/m³, 3.3× its usual 7.7Shawinigan, 3 July: 18.3 µg/m³Shawinigan, 4 July: 13.7 µg/m³Shawinigan, 5 July: 11.4 µg/m³OttawaOttawa, 22 June: 8.0 µg/m³Ottawa, 23 June: 8.8 µg/m³Ottawa, 24 June: 7.7 µg/m³Ottawa, 25 June: 161.0 µg/m³, 21× its usual 7.5Ottawa, 26 June: 83.1 µg/m³, 11× its usual 7.3Ottawa, 27 June: 6.5 µg/m³Ottawa, 28 June: 14.1 µg/m³Ottawa, 29 June: 66.8 µg/m³, 9.7× its usual 6.9Ottawa, 30 June: 69.6 µg/m³, 10× its usual 6.9Ottawa, 1 July: 37.9 µg/m³, 5.5× its usual 6.9Ottawa, 2 July: 16.9 µg/m³Ottawa, 3 July: 19.0 µg/m³Ottawa, 4 July: 15.3 µg/m³Ottawa, 5 July: 14.6 µg/m³Sault Ste. MarieSault Ste. Marie, 22 June: 34.9 µg/m³Sault Ste. Marie, 23 June: 35.5 µg/m³Sault Ste. Marie, 24 June: 22.1 µg/m³Sault Ste. Marie, 25 June: 105.0 µg/m³, 14× its usual 7.3Sault Ste. Marie, 26 June: 82.8 µg/m³, 11× its usual 7.3Sault Ste. Marie, 27 June: 148.0 µg/m³, 21× its usual 7.0Sault Ste. Marie, 28 June: 11.3 µg/m³Sault Ste. Marie, 29 June: 33.4 µg/m³, 4.6× its usual 7.2Sault Ste. Marie, 30 June: 27.4 µg/m³, 3.8× its usual 7.3Sault Ste. Marie, 1 July: 11.5 µg/m³Sault Ste. Marie, 2 July: 8.7 µg/m³Sault Ste. Marie, 3 July: 11.1 µg/m³Sault Ste. Marie, 4 July: 12.5 µg/m³Sault Ste. Marie, 5 July: 9.6 µg/m³Rivière-des-Prairie…Rivière-des-Prairies–Pointe-aux-Trembles, 22 June: 7.7 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 23 June: 7.6 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 24 June: 7.8 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 25 June: 139.5 µg/m³, 19× its usual 7.2Rivière-des-Prairies–Pointe-aux-Trembles, 26 June: 52.9 µg/m³, 7.7× its usual 6.9Rivière-des-Prairies–Pointe-aux-Trembles, 27 June: 3.8 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 28 June: 8.2 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 29 June: 15.0 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 30 June: 49.9 µg/m³, 7.4× its usual 6.7Rivière-des-Prairies–Pointe-aux-Trembles, 1 July: 41.9 µg/m³, 6.3× its usual 6.6Rivière-des-Prairies–Pointe-aux-Trembles, 2 July: 22.5 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 3 July: 15.2 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 4 July: 16.2 µg/m³Rivière-des-Prairies–Pointe-aux-Trembles, 5 July: 14.5 µg/m³BrossardBrossard, 22 June: 7.8 µg/m³Brossard, 23 June: 7.0 µg/m³Brossard, 24 June: 6.5 µg/m³Brossard, 25 June: 138.5 µg/m³, 17× its usual 8.2Brossard, 26 June: 55.1 µg/m³, 6.8× its usual 8.1Brossard, 27 June: 4.4 µg/m³Brossard, 28 June: 9.5 µg/m³Brossard, 29 June: 21.7 µg/m³Brossard, 30 June: 36.5 µg/m³, 4.9× its usual 7.5Brossard, 1 July: 46.7 µg/m³, 6.4× its usual 7.3Brossard, 2 July: 27.4 µg/m³, 3.8× its usual 7.3Brossard, 3 July: 14.2 µg/m³Brossard, 4 July: 15.7 µg/m³Brossard, 5 July: 15.7 µg/m³DrummondvilleDrummondville, 22 June: 7.6 µg/m³Drummondville, 23 June: 8.0 µg/m³Drummondville, 24 June: 6.0 µg/m³Drummondville, 25 June: 133.0 µg/m³, 18× its usual 7.3Drummondville, 26 June: 42.0 µg/m³, 5.8× its usual 7.3Drummondville, 27 June: 3.8 µg/m³Drummondville, 28 June: 8.3 µg/m³Drummondville, 29 June: 10.9 µg/m³Drummondville, 30 June: 22.5 µg/m³Drummondville, 1 July: 38.9 µg/m³, 5.6× its usual 6.9Drummondville, 2 July: 27.7 µg/m³, 4.1× its usual 6.8Drummondville, 3 July: 14.2 µg/m³Drummondville, 4 July: 15.9 µg/m³Drummondville, 5 July: 13.1 µg/m³WaukeshaWaukesha, 22 June: 26.2 µg/m³Waukesha, 23 June: 41.7 µg/m³Waukesha, 24 June: 20.3 µg/m³Waukesha, 25 June: 9.9 µg/m³Waukesha, 26 June: 42.6 µg/m³, 5.4× its usual 7.9Waukesha, 27 June: 191.0 µg/m³, 25× its usual 7.6Waukesha, 28 June: 142.0 µg/m³, 19× its usual 7.5Waukesha, 29 June: 98.4 µg/m³, 13× its usual 7.6Waukesha, 30 June: 37.9 µg/m³, 5.0× its usual 7.6Waukesha, 1 July: 18.5 µg/m³Waukesha, 2 July: 14.9 µg/m³Waukesha, 3 July: 12.2 µg/m³Waukesha, 4 July: 13.9 µg/m³Waukesha, 5 July: 12.5 µg/m³MadisonMadison, 22 June: 21.1 µg/m³Madison, 23 June: 39.5 µg/m³Madison, 24 June: 27.2 µg/m³Madison, 25 June: 8.6 µg/m³Madison, 26 June: 38.0 µg/m³, 5.4× its usual 7.0Madison, 27 June: 123.0 µg/m³, 18× its usual 7.0Madison, 28 June: 182.5 µg/m³, 26× its usual 6.9Madison, 29 June: 135.0 µg/m³, 19× its usual 7.0Madison, 30 June: 20.8 µg/m³Madison, 1 July: 14.4 µg/m³Madison, 2 July: 16.3 µg/m³Madison, 3 July: 13.9 µg/m³Madison, 4 July: 8.5 µg/m³Madison, 5 July: 13.2 µg/m³South MilwaukeeSouth Milwaukee, 22 June: 28.1 µg/m³South Milwaukee, 23 June: 33.3 µg/m³South Milwaukee, 24 June: 15.4 µg/m³South Milwaukee, 25 June: 13.4 µg/m³South Milwaukee, 26 June: 47.1 µg/m³, 6.6× its usual 7.1South Milwaukee, 27 June: 172.0 µg/m³, 25× its usual 7.0South Milwaukee, 28 June: 150.0 µg/m³, 22× its usual 6.9South Milwaukee, 29 June: 92.9 µg/m³, 13× its usual 6.9South Milwaukee, 30 June: no readingSouth Milwaukee, 1 July: 27.4 µg/m³South Milwaukee, 2 July: 23.3 µg/m³South Milwaukee, 3 July: 16.5 µg/m³South Milwaukee, 4 July: 21.1 µg/m³South Milwaukee, 5 July: 17.7 µg/m³JolietJoliet, 22 June: 22.9 µg/m³Joliet, 23 June: 32.8 µg/m³Joliet, 24 June: 23.5 µg/m³Joliet, 25 June: 10.4 µg/m³Joliet, 26 June: 32.7 µg/m³, 3.6× its usual 9.1Joliet, 27 June: 144.0 µg/m³, 16× its usual 9.1Joliet, 28 June: 170.0 µg/m³, 19× its usual 9.1Joliet, 29 June: 66.3 µg/m³, 7.3× its usual 9.1Joliet, 30 June: 26.4 µg/m³, 2.9× its usual 9.1Joliet, 1 July: 17.0 µg/m³Joliet, 2 July: 9.5 µg/m³Joliet, 3 July: 16.0 µg/m³Joliet, 4 July: 20.0 µg/m³Joliet, 5 July: 13.8 µg/m³RockfordRockford, 22 June: 20.6 µg/m³Rockford, 23 June: 40.4 µg/m³Rockford, 24 June: 23.4 µg/m³Rockford, 25 June: 8.5 µg/m³Rockford, 26 June: 32.8 µg/m³, 4.2× its usual 7.9Rockford, 27 June: 133.0 µg/m³, 17× its usual 7.8Rockford, 28 June: 168.0 µg/m³, 22× its usual 7.8Rockford, 29 June: 117.0 µg/m³, 15× its usual 7.9Rockford, 30 June: 33.9 µg/m³, 4.3× its usual 7.9Rockford, 1 July: 16.2 µg/m³Rockford, 2 July: 15.7 µg/m³Rockford, 3 July: 15.8 µg/m³Rockford, 4 July: 18.5 µg/m³Rockford, 5 July: 12.9 µg/m³MilwaukeeMilwaukee, 22 June: 26.9 µg/m³Milwaukee, 23 June: 36.0 µg/m³Milwaukee, 24 June: 14.5 µg/m³Milwaukee, 25 June: 10.9 µg/m³Milwaukee, 26 June: 44.6 µg/m³, 5.2× its usual 8.5Milwaukee, 27 June: 167.0 µg/m³, 20× its usual 8.4Milwaukee, 28 June: 146.0 µg/m³, 17× its usual 8.4Milwaukee, 29 June: 89.0 µg/m³, 11× its usual 8.4Milwaukee, 30 June: 37.0 µg/m³, 4.4× its usual 8.4Milwaukee, 1 July: 19.9 µg/m³Milwaukee, 2 July: 15.4 µg/m³Milwaukee, 3 July: 13.9 µg/m³Milwaukee, 4 July: 26.2 µg/m³Milwaukee, 5 July: 15.6 µg/m³NapervilleNaperville, 22 June: 22.9 µg/m³Naperville, 23 June: 31.6 µg/m³Naperville, 24 June: 22.9 µg/m³Naperville, 25 June: 11.0 µg/m³Naperville, 26 June: 35.2 µg/m³, 3.7× its usual 9.4Naperville, 27 June: 154.0 µg/m³, 17× its usual 9.3Naperville, 28 June: 153.0 µg/m³, 17× its usual 9.2Naperville, 29 June: 70.5 µg/m³, 7.6× its usual 9.3Naperville, 30 June: 28.1 µg/m³, 3.0× its usual 9.4Naperville, 1 July: 17.8 µg/m³Naperville, 2 July: 11.5 µg/m³Naperville, 3 July: no readingNaperville, 4 July: no readingNaperville, 5 July: 17.1 µg/m³CaryCary, 22 June: 21.1 µg/m³Cary, 23 June: 28.2 µg/m³Cary, 24 June: 17.3 µg/m³Cary, 25 June: 9.3 µg/m³Cary, 26 June: 32.6 µg/m³, 3.8× its usual 8.5Cary, 27 June: 149.0 µg/m³, 18× its usual 8.3Cary, 28 June: 122.0 µg/m³, 15× its usual 8.3Cary, 29 June: 80.5 µg/m³, 9.6× its usual 8.4Cary, 30 June: 32.8 µg/m³, 4.0× its usual 8.3Cary, 1 July: 17.4 µg/m³Cary, 2 July: 14.3 µg/m³Cary, 3 July: 13.2 µg/m³Cary, 4 July: 19.3 µg/m³Cary, 5 July: 19.3 µg/m³JenisonJenison, 22 June: no readingJenison, 23 June: no readingJenison, 24 June: no readingJenison, 25 June: no readingJenison, 26 June: 35.0 µg/m³, 4.4× its usual 7.9Jenison, 27 June: 148.0 µg/m³, 19× its usual 7.9Jenison, 28 June: 123.0 µg/m³, 16× its usual 7.9Jenison, 29 June: 89.7 µg/m³, 11× its usual 8.0Jenison, 30 June: 30.7 µg/m³, 3.8× its usual 8.1Jenison, 1 July: 28.2 µg/m³Jenison, 2 July: 17.6 µg/m³Jenison, 3 July: no readingJenison, 4 July: no readingJenison, 5 July: 20.9 µg/m³KalamazooKalamazoo, 22 June: no readingKalamazoo, 23 June: 11.3 µg/m³Kalamazoo, 24 June: 19.7 µg/m³Kalamazoo, 25 June: 16.9 µg/m³Kalamazoo, 26 June: 30.9 µg/m³, 3.3× its usual 9.4Kalamazoo, 27 June: 148.0 µg/m³, 16× its usual 9.2Kalamazoo, 28 June: 119.0 µg/m³, 13× its usual 9.2Kalamazoo, 29 June: 112.0 µg/m³, 12× its usual 9.3Kalamazoo, 30 June: 32.2 µg/m³, 3.3× its usual 9.7Kalamazoo, 1 July: 15.5 µg/m³Kalamazoo, 2 July: no readingKalamazoo, 3 July: no readingKalamazoo, 4 July: 21.3 µg/m³Kalamazoo, 5 July: 24.4 µg/m³South BendSouth Bend, 22 June: 15.6 µg/m³South Bend, 23 June: 7.1 µg/m³South Bend, 24 June: 13.9 µg/m³South Bend, 25 June: 13.6 µg/m³South Bend, 26 June: 25.1 µg/m³, 2.8× its usual 8.9South Bend, 27 June: 146.0 µg/m³, 17× its usual 8.6South Bend, 28 June: 117.0 µg/m³, 14× its usual 8.6South Bend, 29 June: 70.8 µg/m³, 8.0× its usual 8.8South Bend, 30 June: 32.4 µg/m³, 3.6× its usual 8.9South Bend, 1 July: 12.6 µg/m³South Bend, 2 July: 5.0 µg/m³South Bend, 3 July: 11.1 µg/m³South Bend, 4 July: 26.3 µg/m³South Bend, 5 July: 18.1 µg/m³Des PlainesDes Plaines, 22 June: 22.1 µg/m³Des Plaines, 23 June: 28.3 µg/m³Des Plaines, 24 June: 14.6 µg/m³Des Plaines, 25 June: 10.6 µg/m³Des Plaines, 26 June: 33.1 µg/m³, 3.9× its usual 8.4Des Plaines, 27 June: 143.0 µg/m³, 17× its usual 8.3Des Plaines, 28 June: 139.0 µg/m³, 17× its usual 8.3Des Plaines, 29 June: 68.7 µg/m³, 8.2× its usual 8.4Des Plaines, 30 June: 28.7 µg/m³, 3.4× its usual 8.5Des Plaines, 1 July: 21.0 µg/m³Des Plaines, 2 July: 13.8 µg/m³Des Plaines, 3 July: 13.7 µg/m³Des Plaines, 4 July: 28.7 µg/m³Des Plaines, 5 July: 23.3 µg/m³Grand RapidsGrand Rapids, 22 June: 21.2 µg/m³Grand Rapids, 23 June: 10.4 µg/m³Grand Rapids, 24 June: 14.7 µg/m³Grand Rapids, 25 June: 14.5 µg/m³Grand Rapids, 26 June: 26.8 µg/m³, 2.9× its usual 9.2Grand Rapids, 27 June: 142.0 µg/m³, 16× its usual 8.9Grand Rapids, 28 June: 105.0 µg/m³, 12× its usual 8.9Grand Rapids, 29 June: 89.4 µg/m³, 9.8× its usual 9.1Grand Rapids, 30 June: 25.2 µg/m³, 2.7× its usual 9.3Grand Rapids, 1 July: 23.9 µg/m³Grand Rapids, 2 July: 14.2 µg/m³Grand Rapids, 3 July: 15.2 µg/m³Grand Rapids, 4 July: 34.6 µg/m³Grand Rapids, 5 July: 34.8 µg/m³NorthbrookNorthbrook, 22 June: 20.2 µg/m³Northbrook, 23 June: 28.3 µg/m³Northbrook, 24 June: 11.0 µg/m³Northbrook, 25 June: 11.6 µg/m³Northbrook, 26 June: 34.0 µg/m³, 3.9× its usual 8.8Northbrook, 27 June: 129.0 µg/m³, 15× its usual 8.4Northbrook, 28 June: 139.0 µg/m³, 17× its usual 8.4Northbrook, 29 June: 73.9 µg/m³, 8.8× its usual 8.4Northbrook, 30 June: 31.0 µg/m³, 3.7× its usual 8.4Northbrook, 1 July: 23.9 µg/m³Northbrook, 2 July: 18.9 µg/m³Northbrook, 3 July: 11.5 µg/m³Northbrook, 4 July: 23.6 µg/m³Northbrook, 5 July: 28.9 µg/m³Calumet CityCalumet City, 22 June: 22.5 µg/m³Calumet City, 23 June: 25.8 µg/m³Calumet City, 24 June: 18.7 µg/m³Calumet City, 25 June: 10.8 µg/m³Calumet City, 26 June: 32.6 µg/m³, 3.8× its usual 8.6Calumet City, 27 June: 135.0 µg/m³, 16× its usual 8.6Calumet City, 28 June: 119.0 µg/m³, 14× its usual 8.6Calumet City, 29 June: 56.3 µg/m³, 6.5× its usual 8.7Calumet City, 30 June: 25.5 µg/m³, 2.9× its usual 8.7Calumet City, 1 July: 21.3 µg/m³Calumet City, 2 July: 8.5 µg/m³Calumet City, 3 July: 13.6 µg/m³Calumet City, 4 July: 18.6 µg/m³Calumet City, 5 July: 12.4 µg/m³ZionZion, 22 June: 20.8 µg/m³Zion, 23 June: 28.5 µg/m³Zion, 24 June: 10.8 µg/m³Zion, 25 June: 8.1 µg/m³Zion, 26 June: 31.0 µg/m³, 4.8× its usual 6.4Zion, 27 June: 129.0 µg/m³, 20× its usual 6.3Zion, 28 June: 112.0 µg/m³, 18× its usual 6.3Zion, 29 June: 65.0 µg/m³, 10× its usual 6.3Zion, 30 June: 36.9 µg/m³, 5.8× its usual 6.4Zion, 1 July: 18.9 µg/m³Zion, 2 July: 12.1 µg/m³Zion, 3 July: 10.2 µg/m³Zion, 4 July: 18.3 µg/m³Zion, 5 July: 19.0 µg/m³BloomingtonBloomington, 22 June: 20.9 µg/m³Bloomington, 23 June: 39.0 µg/m³Bloomington, 24 June: 24.5 µg/m³Bloomington, 25 June: 10.1 µg/m³Bloomington, 26 June: 19.8 µg/m³Bloomington, 27 June: 111.0 µg/m³, 14× its usual 7.9Bloomington, 28 June: 215.0 µg/m³, 27× its usual 7.9Bloomington, 29 June: 40.7 µg/m³, 5.1× its usual 8.0Bloomington, 30 June: 23.4 µg/m³Bloomington, 1 July: 12.0 µg/m³Bloomington, 2 July: 6.0 µg/m³Bloomington, 3 July: 13.0 µg/m³Bloomington, 4 July: 15.7 µg/m³Bloomington, 5 July: 9.6 µg/m³DecaturDecatur, 22 June: 18.9 µg/m³Decatur, 23 June: 24.8 µg/m³Decatur, 24 June: 24.7 µg/m³Decatur, 25 June: 11.3 µg/m³Decatur, 26 June: 15.9 µg/m³Decatur, 27 June: 87.7 µg/m³, 9.9× its usual 8.9Decatur, 28 June: 214.0 µg/m³, 24× its usual 8.9Decatur, 29 June: 36.9 µg/m³, 4.1× its usual 8.9Decatur, 30 June: 10.8 µg/m³Decatur, 1 July: 7.9 µg/m³Decatur, 2 July: 5.5 µg/m³Decatur, 3 July: 14.6 µg/m³Decatur, 4 July: 16.9 µg/m³Decatur, 5 July: 11.4 µg/m³MedinaMedina, 22 June: 5.0 µg/m³Medina, 23 June: 5.6 µg/m³Medina, 24 June: 5.7 µg/m³Medina, 25 June: 13.7 µg/m³Medina, 26 June: 7.8 µg/m³Medina, 27 June: 42.0 µg/m³, 5.0× its usual 8.4Medina, 28 June: 212.0 µg/m³, 25× its usual 8.4Medina, 29 June: 100.0 µg/m³, 12× its usual 8.4Medina, 30 June: 33.0 µg/m³, 3.9× its usual 8.4Medina, 1 July: 14.0 µg/m³Medina, 2 July: 4.9 µg/m³Medina, 3 July: 5.6 µg/m³Medina, 4 July: 11.4 µg/m³Medina, 5 July: 15.1 µg/m³CantonCanton, 22 June: 5.6 µg/m³Canton, 23 June: 4.5 µg/m³Canton, 24 June: 7.1 µg/m³Canton, 25 June: 18.7 µg/m³Canton, 26 June: 9.4 µg/m³Canton, 27 June: 34.3 µg/m³, 3.4× its usual 10.0Canton, 28 June: 209.0 µg/m³, 21× its usual 10.0Canton, 29 June: 152.5 µg/m³, 15× its usual 10.0Canton, 30 June: 37.1 µg/m³, 3.7× its usual 10.0Canton, 1 July: 13.3 µg/m³Canton, 2 July: 5.9 µg/m³Canton, 3 July: 7.1 µg/m³Canton, 4 July: 22.2 µg/m³Canton, 5 July: 30.1 µg/m³AkronAkron, 22 June: 4.7 µg/m³Akron, 23 June: 4.9 µg/m³Akron, 24 June: 6.0 µg/m³Akron, 25 June: 15.6 µg/m³Akron, 26 June: 8.0 µg/m³Akron, 27 June: 37.1 µg/m³, 4.7× its usual 7.9Akron, 28 June: 172.0 µg/m³, 22× its usual 7.9Akron, 29 June: 95.9 µg/m³, 12× its usual 7.9Akron, 30 June: 33.2 µg/m³, 4.2× its usual 7.9Akron, 1 July: 11.0 µg/m³Akron, 2 July: 5.1 µg/m³Akron, 3 July: 5.3 µg/m³Akron, 4 July: 22.6 µg/m³Akron, 5 July: 26.1 µg/m³SpringfieldSpringfield, 22 June: 18.8 µg/m³Springfield, 23 June: 21.0 µg/m³Springfield, 24 June: 21.1 µg/m³Springfield, 25 June: 9.2 µg/m³Springfield, 26 June: 10.5 µg/m³Springfield, 27 June: 62.4 µg/m³, 6.7× its usual 9.3Springfield, 28 June: 170.0 µg/m³, 18× its usual 9.3Springfield, 29 June: no readingSpringfield, 30 June: 12.0 µg/m³Springfield, 1 July: 7.1 µg/m³Springfield, 2 July: 5.4 µg/m³Springfield, 3 July: 17.5 µg/m³Springfield, 4 July: 22.4 µg/m³Springfield, 5 July: 11.4 µg/m³IndianapolisIndianapolis, 22 June: 8.6 µg/m³Indianapolis, 23 June: 8.5 µg/m³Indianapolis, 24 June: 16.9 µg/m³Indianapolis, 25 June: 19.5 µg/m³Indianapolis, 26 June: 14.2 µg/m³Indianapolis, 27 June: 103.0 µg/m³, 9.7× its usual 10.6Indianapolis, 28 June: 168.0 µg/m³, 16× its usual 10.4Indianapolis, 29 June: 72.8 µg/m³, 7.0× its usual 10.4Indianapolis, 30 June: 9.9 µg/m³Indianapolis, 1 July: 7.3 µg/m³Indianapolis, 2 July: 6.3 µg/m³Indianapolis, 3 July: 11.2 µg/m³Indianapolis, 4 July: 35.6 µg/m³Indianapolis, 5 July: 33.7 µg/m³ClintonClinton, 22 June: 19.0 µg/m³Clinton, 23 June: 27.4 µg/m³Clinton, 24 June: 23.4 µg/m³Clinton, 25 June: 6.9 µg/m³Clinton, 26 June: 22.3 µg/m³Clinton, 27 June: 111.0 µg/m³, 15× its usual 7.4Clinton, 28 June: 160.0 µg/m³, 21× its usual 7.6Clinton, 29 June: 94.2 µg/m³, 12× its usual 7.6Clinton, 30 June: 23.4 µg/m³Clinton, 1 July: 14.3 µg/m³Clinton, 2 July: 12.9 µg/m³Clinton, 3 July: 14.9 µg/m³Clinton, 4 July: 15.5 µg/m³Clinton, 5 July: 12.6 µg/m³Terre HauteTerre Haute, 22 June: 10.1 µg/m³Terre Haute, 23 June: 8.3 µg/m³Terre Haute, 24 June: 20.3 µg/m³Terre Haute, 25 June: 12.6 µg/m³Terre Haute, 26 June: 9.8 µg/m³Terre Haute, 27 June: 67.8 µg/m³, 6.2× its usual 11.0Terre Haute, 28 June: 160.0 µg/m³, 15× its usual 10.7Terre Haute, 29 June: no readingTerre Haute, 30 June: no readingTerre Haute, 1 July: no readingTerre Haute, 2 July: no readingTerre Haute, 3 July: 12.5 µg/m³Terre Haute, 4 July: 31.3 µg/m³Terre Haute, 5 July: 21.6 µg/m³ClevelandCleveland, 22 June: 6.0 µg/m³Cleveland, 23 June: 5.6 µg/m³Cleveland, 24 June: 6.0 µg/m³Cleveland, 25 June: 15.9 µg/m³Cleveland, 26 June: 9.6 µg/m³Cleveland, 27 June: 51.7 µg/m³, 4.9× its usual 10.6Cleveland, 28 June: 160.0 µg/m³, 15× its usual 10.6Cleveland, 29 June: 83.6 µg/m³, 7.9× its usual 10.6Cleveland, 30 June: 35.5 µg/m³, 3.3× its usual 10.6Cleveland, 1 July: 15.8 µg/m³Cleveland, 2 July: 7.9 µg/m³Cleveland, 3 July: 5.8 µg/m³Cleveland, 4 July: 18.4 µg/m³Cleveland, 5 July: 25.6 µg/m³BloomingtonBloomington, 22 June: 6.9 µg/m³Bloomington, 23 June: 4.8 µg/m³Bloomington, 24 June: 22.7 µg/m³Bloomington, 25 June: 13.9 µg/m³Bloomington, 26 June: 8.9 µg/m³Bloomington, 27 June: 55.4 µg/m³, 7.0× its usual 7.9Bloomington, 28 June: 159.0 µg/m³, 20× its usual 7.9Bloomington, 29 June: 44.6 µg/m³, 5.6× its usual 8.0Bloomington, 30 June: 7.6 µg/m³Bloomington, 1 July: 7.0 µg/m³Bloomington, 2 July: 5.0 µg/m³Bloomington, 3 July: 9.3 µg/m³Bloomington, 4 July: 16.9 µg/m³Bloomington, 5 July: 13.6 µg/m³MolineMoline, 22 June: 20.2 µg/m³Moline, 23 June: 22.7 µg/m³Moline, 24 June: 21.4 µg/m³Moline, 25 June: 7.8 µg/m³Moline, 26 June: 19.4 µg/m³Moline, 27 June: 115.0 µg/m³, 15× its usual 7.5Moline, 28 June: 155.0 µg/m³, 20× its usual 7.6Moline, 29 June: 86.4 µg/m³, 11× its usual 7.6Moline, 30 June: 21.7 µg/m³Moline, 1 July: 12.6 µg/m³Moline, 2 July: 13.5 µg/m³Moline, 3 July: 15.9 µg/m³Moline, 4 July: 19.0 µg/m³Moline, 5 July: 12.8 µg/m³Lincoln ParkLincoln Park, 22 June: 11.6 µg/m³Lincoln Park, 23 June: 4.3 µg/m³Lincoln Park, 24 June: 6.4 µg/m³Lincoln Park, 25 June: 12.9 µg/m³Lincoln Park, 26 June: 8.3 µg/m³Lincoln Park, 27 June: 87.6 µg/m³, 9.8× its usual 8.9Lincoln Park, 28 June: 155.0 µg/m³, 17× its usual 8.9Lincoln Park, 29 June: 103.0 µg/m³, 11× its usual 9.0Lincoln Park, 30 June: 35.0 µg/m³, 3.9× its usual 9.0Lincoln Park, 1 July: 17.6 µg/m³Lincoln Park, 2 July: 6.0 µg/m³Lincoln Park, 3 July: 9.2 µg/m³Lincoln Park, 4 July: 21.4 µg/m³Lincoln Park, 5 July: 18.4 µg/m³YoungstownYoungstown, 22 June: no readingYoungstown, 23 June: no readingYoungstown, 24 June: 6.9 µg/m³Youngstown, 25 June: 14.3 µg/m³Youngstown, 26 June: 10.8 µg/m³Youngstown, 27 June: 27.5 µg/m³, 3.2× its usual 8.5Youngstown, 28 June: 152.0 µg/m³, 18× its usual 8.4Youngstown, 29 June: 105.0 µg/m³, 13× its usual 8.4Youngstown, 30 June: 50.7 µg/m³, 6.0× its usual 8.4Youngstown, 1 July: 11.5 µg/m³Youngstown, 2 July: 7.1 µg/m³Youngstown, 3 July: 5.4 µg/m³Youngstown, 4 July: 12.3 µg/m³Youngstown, 5 July: 21.9 µg/m³TaylorTaylor, 22 June: 11.5 µg/m³Taylor, 23 June: 4.4 µg/m³Taylor, 24 June: 8.5 µg/m³Taylor, 25 June: 13.6 µg/m³Taylor, 26 June: 10.3 µg/m³Taylor, 27 June: 89.2 µg/m³, 11× its usual 8.3Taylor, 28 June: 148.0 µg/m³, 18× its usual 8.3Taylor, 29 June: 108.0 µg/m³, 13× its usual 8.3Taylor, 30 June: 38.1 µg/m³, 4.6× its usual 8.3Taylor, 1 July: 19.4 µg/m³Taylor, 2 July: 6.8 µg/m³Taylor, 3 July: 11.2 µg/m³Taylor, 4 July: 18.2 µg/m³Taylor, 5 July: 16.1 µg/m³WarrenWarren, 22 June: 5.0 µg/m³Warren, 23 June: 5.8 µg/m³Warren, 24 June: 8.4 µg/m³Warren, 25 June: 16.1 µg/m³Warren, 26 June: 11.5 µg/m³Warren, 27 June: 33.9 µg/m³, 3.5× its usual 9.8Warren, 28 June: 147.0 µg/m³, 15× its usual 9.7Warren, 29 June: 97.9 µg/m³, 10.0× its usual 9.8Warren, 30 June: 49.0 µg/m³, 5.1× its usual 9.7Warren, 1 July: 13.8 µg/m³Warren, 2 July: 8.0 µg/m³Warren, 3 July: 6.1 µg/m³Warren, 4 July: 15.2 µg/m³Warren, 5 July: 26.0 µg/m³Shaker HeightsShaker Heights, 22 June: 4.5 µg/m³Shaker Heights, 23 June: 5.1 µg/m³Shaker Heights, 24 June: 6.7 µg/m³Shaker Heights, 25 June: 10.4 µg/m³Shaker Heights, 26 June: 8.4 µg/m³Shaker Heights, 27 June: 46.4 µg/m³, 6.0× its usual 7.7Shaker Heights, 28 June: 144.0 µg/m³, 19× its usual 7.7Shaker Heights, 29 June: 74.2 µg/m³, 9.6× its usual 7.7Shaker Heights, 30 June: 35.2 µg/m³, 4.6× its usual 7.7Shaker Heights, 1 July: 12.0 µg/m³Shaker Heights, 2 July: 6.2 µg/m³Shaker Heights, 3 July: 5.2 µg/m³Shaker Heights, 4 July: 10.8 µg/m³Shaker Heights, 5 July: 14.8 µg/m³DavenportDavenport, 22 June: 18.8 µg/m³Davenport, 23 June: 22.3 µg/m³Davenport, 24 June: 19.5 µg/m³Davenport, 25 June: 6.8 µg/m³Davenport, 26 June: 16.7 µg/m³Davenport, 27 June: 102.0 µg/m³, 14× its usual 7.4Davenport, 28 June: 143.0 µg/m³, 19× its usual 7.4Davenport, 29 June: 79.0 µg/m³, 10× its usual 7.6Davenport, 30 June: 20.4 µg/m³Davenport, 1 July: 11.9 µg/m³Davenport, 2 July: 10.8 µg/m³Davenport, 3 July: 17.3 µg/m³Davenport, 4 July: 23.4 µg/m³Davenport, 5 July: 12.3 µg/m³DearbornDearborn, 22 June: 12.9 µg/m³Dearborn, 23 June: 6.5 µg/m³Dearborn, 24 June: 8.6 µg/m³Dearborn, 25 June: 14.3 µg/m³Dearborn, 26 June: 11.3 µg/m³Dearborn, 27 June: 99.1 µg/m³, 10× its usual 9.5Dearborn, 28 June: 143.0 µg/m³, 15× its usual 9.5Dearborn, 29 June: 104.0 µg/m³, 11× its usual 9.5Dearborn, 30 June: 38.4 µg/m³, 4.0× its usual 9.5Dearborn, 1 July: 21.2 µg/m³Dearborn, 2 July: 8.1 µg/m³Dearborn, 3 July: 10.7 µg/m³Dearborn, 4 July: 19.1 µg/m³Dearborn, 5 July: 17.8 µg/m³WindsorWindsor, 22 June: 11.7 µg/m³Windsor, 23 June: 3.4 µg/m³Windsor, 24 June: 6.6 µg/m³Windsor, 25 June: 10.0 µg/m³Windsor, 26 June: 7.9 µg/m³Windsor, 27 June: 88.0 µg/m³, 9.7× its usual 9.1Windsor, 28 June: 141.0 µg/m³, 16× its usual 9.0Windsor, 29 June: 105.0 µg/m³, 12× its usual 9.1Windsor, 30 June: 35.6 µg/m³, 3.9× its usual 9.2Windsor, 1 July: 17.3 µg/m³Windsor, 2 July: 6.2 µg/m³Windsor, 3 July: 8.6 µg/m³Windsor, 4 July: 12.5 µg/m³Windsor, 5 July: 14.8 µg/m³ColumbusColumbus, 22 June: 4.3 µg/m³Columbus, 23 June: 4.2 µg/m³Columbus, 24 June: 18.0 µg/m³Columbus, 25 June: 13.4 µg/m³Columbus, 26 June: 6.4 µg/m³Columbus, 27 June: 47.9 µg/m³, 5.7× its usual 8.4Columbus, 28 June: 141.0 µg/m³, 17× its usual 8.5Columbus, 29 June: 52.0 µg/m³, 6.0× its usual 8.6Columbus, 30 June: 9.3 µg/m³Columbus, 1 July: no readingColumbus, 2 July: 3.8 µg/m³Columbus, 3 July: 6.2 µg/m³Columbus, 4 July: 12.7 µg/m³Columbus, 5 July: 15.3 µg/m³DetroitDetroit, 22 June: 13.6 µg/m³Detroit, 23 June: 4.4 µg/m³Detroit, 24 June: 6.9 µg/m³Detroit, 25 June: 11.0 µg/m³Detroit, 26 June: 9.8 µg/m³Detroit, 27 June: 82.1 µg/m³, 9.0× its usual 9.1Detroit, 28 June: 135.5 µg/m³, 15× its usual 9.1Detroit, 29 June: 98.4 µg/m³, 11× its usual 9.1Detroit, 30 June: 35.9 µg/m³, 3.8× its usual 9.4Detroit, 1 July: 18.6 µg/m³Detroit, 2 July: 7.0 µg/m³Detroit, 3 July: 10.5 µg/m³Detroit, 4 July: 15.4 µg/m³Detroit, 5 July: 16.7 µg/m³Iowa CityIowa City, 22 June: 20.4 µg/m³Iowa City, 23 June: 20.7 µg/m³Iowa City, 24 June: 18.3 µg/m³Iowa City, 25 June: 7.4 µg/m³Iowa City, 26 June: 11.3 µg/m³Iowa City, 27 June: 118.0 µg/m³, 16× its usual 7.6Iowa City, 28 June: 135.0 µg/m³, 18× its usual 7.6Iowa City, 29 June: 112.0 µg/m³, 15× its usual 7.7Iowa City, 30 June: 25.5 µg/m³, 3.3× its usual 7.8Iowa City, 1 July: 9.7 µg/m³Iowa City, 2 July: 10.5 µg/m³Iowa City, 3 July: 15.2 µg/m³Iowa City, 4 July: 13.8 µg/m³Iowa City, 5 July: 12.6 µg/m³DublinDublin, 22 June: 5.2 µg/m³Dublin, 23 June: 4.8 µg/m³Dublin, 24 June: 5.5 µg/m³Dublin, 25 June: 15.4 µg/m³Dublin, 26 June: 7.6 µg/m³Dublin, 27 June: 65.4 µg/m³, 8.1× its usual 8.1Dublin, 28 June: 134.0 µg/m³, 17× its usual 8.1Dublin, 29 June: 106.0 µg/m³, 13× its usual 8.4Dublin, 30 June: 11.2 µg/m³Dublin, 1 July: 9.0 µg/m³Dublin, 2 July: 6.0 µg/m³Dublin, 3 July: 5.3 µg/m³Dublin, 4 July: 13.7 µg/m³Dublin, 5 July: 26.6 µg/m³Port HuronPort Huron, 22 June: 15.5 µg/m³Port Huron, 23 June: 8.5 µg/m³Port Huron, 24 June: 10.4 µg/m³Port Huron, 25 June: 14.2 µg/m³Port Huron, 26 June: 7.6 µg/m³Port Huron, 27 June: 104.0 µg/m³, 12× its usual 8.4Port Huron, 28 June: 132.0 µg/m³, 16× its usual 8.4Port Huron, 29 June: 68.5 µg/m³, 8.2× its usual 8.4Port Huron, 30 June: 47.8 µg/m³, 5.6× its usual 8.6Port Huron, 1 July: 22.9 µg/m³Port Huron, 2 July: 10.4 µg/m³Port Huron, 3 July: 9.3 µg/m³Port Huron, 4 July: 18.7 µg/m³Port Huron, 5 July: 15.1 µg/m³MuscatineMuscatine, 22 June: 19.7 µg/m³Muscatine, 23 June: 20.7 µg/m³Muscatine, 24 June: 18.7 µg/m³Muscatine, 25 June: 5.6 µg/m³Muscatine, 26 June: 11.6 µg/m³Muscatine, 27 June: 89.5 µg/m³, 15× its usual 6.0Muscatine, 28 June: 131.0 µg/m³, 22× its usual 6.0Muscatine, 29 June: 87.4 µg/m³, 15× its usual 6.0Muscatine, 30 June: 16.3 µg/m³Muscatine, 1 July: 6.8 µg/m³Muscatine, 2 July: 10.6 µg/m³Muscatine, 3 July: 18.9 µg/m³Muscatine, 4 July: 15.3 µg/m³Muscatine, 5 July: 12.6 µg/m³WilkinsburgWilkinsburg, 22 June: no readingWilkinsburg, 23 June: 4.3 µg/m³Wilkinsburg, 24 June: 6.2 µg/m³Wilkinsburg, 25 June: 12.1 µg/m³Wilkinsburg, 26 June: 11.5 µg/m³Wilkinsburg, 27 June: 19.1 µg/m³Wilkinsburg, 28 June: 118.0 µg/m³, 13× its usual 9.1Wilkinsburg, 29 June: 164.0 µg/m³, 18× its usual 9.1Wilkinsburg, 30 June: 54.8 µg/m³, 6.0× its usual 9.1Wilkinsburg, 1 July: 13.6 µg/m³Wilkinsburg, 2 July: 10.1 µg/m³Wilkinsburg, 3 July: 6.6 µg/m³Wilkinsburg, 4 July: 17.2 µg/m³Wilkinsburg, 5 July: 32.3 µg/m³PittsburghPittsburgh, 22 June: 3.6 µg/m³Pittsburgh, 23 June: 4.0 µg/m³Pittsburgh, 24 June: 6.8 µg/m³Pittsburgh, 25 June: 13.0 µg/m³Pittsburgh, 26 June: 11.6 µg/m³Pittsburgh, 27 June: 19.2 µg/m³Pittsburgh, 28 June: 115.5 µg/m³, 12× its usual 9.6Pittsburgh, 29 June: 152.0 µg/m³, 16× its usual 9.6Pittsburgh, 30 June: 53.6 µg/m³, 5.6× its usual 9.6Pittsburgh, 1 July: 13.4 µg/m³Pittsburgh, 2 July: 9.5 µg/m³Pittsburgh, 3 July: 6.5 µg/m³Pittsburgh, 4 July: 11.9 µg/m³Pittsburgh, 5 July: 21.3 µg/m³SteubenvilleSteubenville, 22 June: 3.3 µg/m³Steubenville, 23 June: 3.7 µg/m³Steubenville, 24 June: 5.2 µg/m³Steubenville, 25 June: 14.8 µg/m³Steubenville, 26 June: 10.2 µg/m³Steubenville, 27 June: 24.0 µg/m³Steubenville, 28 June: 147.0 µg/m³, 14× its usual 10.2Steubenville, 29 June: 147.0 µg/m³, 14× its usual 10.3Steubenville, 30 June: 38.1 µg/m³, 3.7× its usual 10.3Steubenville, 1 July: 11.6 µg/m³Steubenville, 2 July: 8.1 µg/m³Steubenville, 3 July: 5.6 µg/m³Steubenville, 4 July: 8.3 µg/m³Steubenville, 5 July: 15.3 µg/m³YpsilantiYpsilanti, 22 June: 14.1 µg/m³Ypsilanti, 23 June: 4.8 µg/m³Ypsilanti, 24 June: 7.9 µg/m³Ypsilanti, 25 June: 11.8 µg/m³Ypsilanti, 26 June: no readingYpsilanti, 27 June: no readingYpsilanti, 28 June: 143.0 µg/m³, 18× its usual 8.0Ypsilanti, 29 June: 108.0 µg/m³, 14× its usual 8.0Ypsilanti, 30 June: 44.0 µg/m³, 5.4× its usual 8.1Ypsilanti, 1 July: 19.2 µg/m³Ypsilanti, 2 July: 5.2 µg/m³Ypsilanti, 3 July: 8.8 µg/m³Ypsilanti, 4 July: 19.0 µg/m³Ypsilanti, 5 July: 19.2 µg/m³AltoonaAltoona, 22 June: 3.0 µg/m³Altoona, 23 June: 4.7 µg/m³Altoona, 24 June: 7.1 µg/m³Altoona, 25 June: 6.7 µg/m³Altoona, 26 June: 7.9 µg/m³Altoona, 27 June: 9.8 µg/m³Altoona, 28 June: 80.0 µg/m³, 9.5× its usual 8.4Altoona, 29 June: 137.0 µg/m³, 16× its usual 8.5Altoona, 30 June: 76.3 µg/m³, 9.1× its usual 8.4Altoona, 1 July: 13.9 µg/m³Altoona, 2 July: 9.8 µg/m³Altoona, 3 July: 7.7 µg/m³Altoona, 4 July: 8.6 µg/m³Altoona, 5 July: 8.7 µg/m³LafayetteLafayette, 22 June: 11.6 µg/m³Lafayette, 23 June: 10.9 µg/m³Lafayette, 24 June: 18.5 µg/m³Lafayette, 25 June: 15.3 µg/m³Lafayette, 26 June: no readingLafayette, 27 June: no readingLafayette, 28 June: 133.0 µg/m³, 15× its usual 8.6Lafayette, 29 June: 48.9 µg/m³, 5.6× its usual 8.8Lafayette, 30 June: 12.6 µg/m³Lafayette, 1 July: 9.7 µg/m³Lafayette, 2 July: 6.0 µg/m³Lafayette, 3 July: 16.2 µg/m³Lafayette, 4 July: 21.0 µg/m³Lafayette, 5 July: 16.0 µg/m³Weirton HeightsWeirton Heights, 22 June: no readingWeirton Heights, 23 June: no readingWeirton Heights, 24 June: no readingWeirton Heights, 25 June: no readingWeirton Heights, 26 June: no readingWeirton Heights, 27 June: 22.6 µg/m³Weirton Heights, 28 June: 132.0 µg/m³, 18× its usual 7.4Weirton Heights, 29 June: 124.0 µg/m³, 17× its usual 7.4Weirton Heights, 30 June: 35.8 µg/m³, 4.8× its usual 7.4Weirton Heights, 1 July: 10.9 µg/m³Weirton Heights, 2 July: 7.9 µg/m³Weirton Heights, 3 July: 5.3 µg/m³Weirton Heights, 4 July: 6.2 µg/m³Weirton Heights, 5 July: 8.7 µg/m³West MifflinWest Mifflin, 22 June: 3.3 µg/m³West Mifflin, 23 June: 6.3 µg/m³West Mifflin, 24 June: 11.5 µg/m³West Mifflin, 25 June: 16.3 µg/m³West Mifflin, 26 June: 13.5 µg/m³West Mifflin, 27 June: 17.4 µg/m³West Mifflin, 28 June: 98.5 µg/m³, 8.9× its usual 11.1West Mifflin, 29 June: 126.5 µg/m³, 11× its usual 11.1West Mifflin, 30 June: 52.5 µg/m³, 4.7× its usual 11.1West Mifflin, 1 July: 19.0 µg/m³West Mifflin, 2 July: 11.3 µg/m³West Mifflin, 3 July: 12.0 µg/m³West Mifflin, 4 July: 14.2 µg/m³West Mifflin, 5 July: 33.6 µg/m³22 Jun242628301 Jul24
The 60 cities with the highest readings of 280, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
North BayOntario, Canada6 397.025 June7.553×
SaguenayQuebec, Canada2 453.025 June9.448×
Rouyn-NorandaQuebec, Canada4 312.026 June7.641×
Greater SudburyOntario, Canada4 275.025 June8.034×
BloomingtonIllinois, United States3 215.028 June7.927×
MadisonWisconsin, United States4 182.528 June6.926×
MedinaOhio, United States4 212.028 June8.425×
WaukeshaWisconsin, United States5 191.027 June7.625×
South MilwaukeeWisconsin, United States4 172.027 June7.025×
DecaturIllinois, United States3 214.028 June8.924×
ShawiniganQuebec, Canada5 192.025 June8.323×
AkronOhio, United States4 172.028 June7.922×
MuscatineIowa, United States3 131.028 June6.022×
RockfordIllinois, United States5 168.028 June7.822×
OttawaOntario, Canada5 161.025 June7.522×
ClintonIowa, United States3 160.028 June7.621×
Sault Ste. MarieOntario, Canada5 148.027 June7.021×
CantonOhio, United States4 209.028 June10.021×
ZionIllinois, United States5 129.027 June6.321×
MolineIllinois, United States3 155.028 June7.620×
BloomingtonIndiana, United States3 159.028 June7.920×
MilwaukeeWisconsin, United States5 167.027 June8.420×
Rivière-des-Prairies–Pointe-aux-TremblesQuebec, Canada4 139.525 June7.219×
DavenportIowa, United States3 143.028 June7.419×
JolietIllinois, United States5 170.028 June9.119×
JenisonMichigan, United States5 148.027 June7.919×
Shaker HeightsOhio, United States4 144.028 June7.719×
ChathamOntario, Canada4 125.028 June6.818×
SpringfieldIllinois, United States2 170.028 June9.318×
DrummondvilleQuebec, Canada4 133.025 June7.318×
YoungstownOhio, United States4 152.028 June8.418×
WilkinsburgPennsylvania, United States3 164.029 June9.118×
CaryIllinois, United States5 149.027 June8.318×
YpsilantiMichigan, United States3 143.028 June8.018×
TaylorMichigan, United States4 148.028 June8.318×
Iowa CityIowa, United States4 135.028 June7.618×
Weirton HeightsWest Virginia, United States3 132.028 June7.418×
Saint-Jean-sur-RichelieuQuebec, Canada4 113.025 June6.418×
Lincoln ParkMichigan, United States4 155.028 June8.917×
Des PlainesIllinois, United States5 143.027 June8.317×
South BendIndiana, United States5 146.027 June8.617×
BrossardQuebec, Canada5 138.525 June8.217×
HermitagePennsylvania, United States4 122.028 June7.217×
NapervilleIllinois, United States5 154.027 June9.317×
ColumbusIndiana, United States3 141.028 June8.517×
NorthbrookIllinois, United States5 139.028 June8.417×
DublinOhio, United States3 134.028 June8.117×
IndianapolisIndiana, United States3 168.028 June10.416×
DorvalQuebec, Canada4 120.025 June7.416×
KalamazooMichigan, United States5 148.027 June9.216×
AltoonaPennsylvania, United States3 137.029 June8.516×
Grand RapidsMichigan, United States5 142.027 June8.916×
BellevilleOntario, Canada4 104.029 June6.516×
East ChicagoIndiana, United States5 121.027 June7.616×
KokomoIndiana, United States3 121.028 June7.616×
PittsburghPennsylvania, United States3 152.029 June9.616×
MontréalQuebec, Canada4 126.025 June8.016×
GranbyQuebec, Canada5 122.025 June7.716×
WindsorOntario, Canada4 141.028 June9.016×
Calumet CityIllinois, United States5 135.027 June8.616×
Port HuronMichigan, United States4 132.028 June8.416×
LafayetteIndiana, United States2 133.028 June8.616×
WarrenOhio, United States4 147.028 June9.715×
ClevelandOhio, United States4 160.028 June10.615×
DearbornMichigan, United States4 143.028 June9.515×
HagerstownMaryland, United States4 84.329 June5.615×
Terre HauteIndiana, United States2 160.028 June10.715×
AppletonWisconsin, United States4 105.028 June7.015×
DetroitMichigan, United States4 135.528 June9.115×
JohnstownPennsylvania, United States3 118.029 June8.015×
GahannaOhio, United States3 108.028 June7.315×
Fort ThomasKentucky, United States3 110.028 June7.515×
AndersonIndiana, United States3 120.028 June8.215×
St. CatharinesOntario, Canada3 106.028 June7.315×
SteubenvilleOhio, United States3 147.028 June10.214×
Trois-RivièresQuebec, Canada2 109.025 June7.714×
HammondIndiana, United States4 126.027 June9.014×
SarniaOntario, Canada4 116.028 June8.314×
EriePennsylvania, United States4 99.728 June7.114×
LansingMichigan, United States4 117.029 June8.514×
State CollegePennsylvania, United States4 98.229 June7.114×
NewburghNew York, United States3 71.230 June5.214×
McKeesportPennsylvania, United States3 116.029 June8.514×
Bay CityMichigan, United States4 106.027 June7.814×
WaterlooIowa, United States3 102.028 June7.514×
LebanonOhio, United States3 104.028 June7.714×
White OakOhio, United States3 92.528 June6.913×
PainesvilleOhio, United States4 87.428 June6.713×
CornwallOntario, Canada5 95.825 June7.413×
Green BayWisconsin, United States5 94.227 June7.313×
SyracuseNew York, United States4 87.629 June6.813×
HollandMichigan, United States5 114.028 June8.913×
MasonOhio, United States3 104.028 June8.113×
ElkhartIndiana, United States4 115.027 June9.113×
DaytonOhio, United States3 121.028 June9.713×
SpringfieldOhio, United States3 121.028 June9.713×
BaltimoreMaryland, United States4 94.529 June7.712×
RochesterNew York, United States4 88.930 June7.212×
CarlislePennsylvania, United States4 92.929 June7.612×
Franklin ParkIllinois, United States5 116.027 June9.612×
ElktonMaryland, United States4 83.229 June6.912×
UticaNew York, United States3 63.529 June5.312×
Rose HillVirginia, United States4 93.229 June7.812×
FlintMichigan, United States4 88.227 June7.512×
BearDelaware, United States4 84.029 June7.212×
RedfordMichigan, United States4 116.028 June10.012×
JeffersonvilleIndiana, United States3 100.028 June8.612×
WilmingtonDelaware, United States4 85.729 June7.412×
PeterboroughOntario, Canada4 78.630 June6.812×
L'Ancienne-LoretteQuebec, Canada3 97.525 June8.512×
West MifflinPennsylvania, United States3 126.529 June11.111×
South LaurelMaryland, United States4 84.229 June7.411×
YorkPennsylvania, United States4 92.829 June8.211×
QuébecQuebec, Canada2 83.925 June7.411×
ChesterPennsylvania, United States4 83.529 June7.411×
Hunt ValleyMaryland, United States3 82.629 June7.311×
ToledoOhio, United States3 110.028 June9.811×
LancasterPennsylvania, United States4 92.229 June8.211×
BethlehemPennsylvania, United States3 78.530 June7.111×
FishersIndiana, United States3 113.028 June10.311×
PortageIndiana, United States5 95.827 June8.711×
SpringfieldVirginia, United States4 90.429 June8.211×
EdgewoodMaryland, United States3 83.429 June7.611×
Lexington-FayetteKentucky, United States2 77.228 June7.011×
CincinnatiOhio, United States3 116.028 June10.611×
ReadingPennsylvania, United States4 84.229 June7.711×
LimaOhio, United States3 117.028 June10.811×
EvansvilleIndiana, United States3 95.228 June8.811×
ScrantonPennsylvania, United States3 92.530 June8.611×
KenmoreNew York, United States2 77.930 June7.211×
La CrosseWisconsin, United States3 95.128 June8.911×
KingstonOntario, Canada4 77.129 June7.211×
HarrisburgPennsylvania, United States4 95.629 June9.111×
MiddletownOhio, United States3 118.528 June11.410×
GaryIndiana, United States5 96.827 June9.310×
St. ThomasOntario, Canada3 82.428 June7.910×
AnkenyIowa, United States3 82.228 June7.910×
RockvilleMaryland, United States3 74.729 June7.210×
ChicagoIllinois, United States3 91.728 June8.910×
NewarkDelaware, United States4 86.529 June8.410×
CharlottesvilleVirginia, United States3 79.629 June7.710×
New AlbanyIndiana, United States2 75.328 June7.310×
Eau ClaireWisconsin, United States4 74.227 June7.210×
NorwoodOhio, United States3 111.028 June11.010×
RochesterMinnesota, United States3 76.828 June7.610×
New CityNew York, United States3 57.330 June5.710×
LebanonPennsylvania, United States4 85.729 June8.610×
Saint MatthewsKentucky, United States3 80.928 June8.110×
AllentownPennsylvania, United States3 76.729 June7.710×
JeffersontownKentucky, United States3 84.428 June8.59.9×
Des MoinesIowa, United States3 72.828 June7.69.6×
BarrieOntario, Canada5 79.728 June8.49.5×
GreenfieldMassachusetts, United States3 60.51 July6.49.5×
BayonneNew Jersey, United States2 49.330 June5.29.5×
BuffaloNew York, United States4 83.530 June8.99.4×
Oak LawnIllinois, United States3 79.227 June8.49.4×
NorristownPennsylvania, United States4 73.829 June7.99.3×
Saint CloudMinnesota, United States2 60.228 June6.59.3×
LouisvilleKentucky, United States3 83.528 June9.19.2×
HamiltonOntario, Canada3 78.330 June8.69.1×
BurnsvilleMinnesota, United States3 67.128 June7.49.1×
Apple ValleyMinnesota, United States3 61.428 June6.89.0×
Saint MichaelMinnesota, United States3 60.128 June6.79.0×
ScaggsvilleMaryland, United States4 87.629 June10.18.7×
OwensboroKentucky, United States3 82.228 June9.48.7×
AshlandKentucky, United States3 65.928 June7.78.6×
LemayMissouri, United States1 61.728 June7.28.6×
WashingtonDistrict of Columbia, United States4 79.629 June9.48.5×
BrantfordOntario, Canada3 71.928 June8.58.5×
RichmondVirginia, United States4 66.329 June7.88.5×
RoanokeVirginia, United States3 66.229 June7.88.5×
ShakopeeMinnesota, United States3 62.228 June7.38.5×
University CityMissouri, United States1 61.528 June7.38.4×
LondonOntario, Canada4 71.327 June8.68.3×
BensalemPennsylvania, United States4 70.029 June8.58.2×
DoverDelaware, United States3 68.929 June8.48.2×
New BrunswickNew Jersey, United States3 66.930 June8.28.2×
WorcesterMassachusetts, United States2 54.01 July6.68.2×
PawtucketRhode Island, United States2 44.41 July5.58.1×
MinneapolisMinnesota, United States3 61.028 June7.68.0×
RutlandVermont, United States2 54.41 July6.88.0×
KitchenerOntario, Canada3 67.028 June8.57.9×
BlaineMinnesota, United States2 49.728 June6.37.9×
PittsfieldMassachusetts, United States3 54.81 July7.07.8×
North ChicopeeMassachusetts, United States2 48.31 July6.27.8×
White PlainsNew York, United States2 46.630 June6.07.8×
HopewellVirginia, United States3 55.829 June7.27.7×
DuluthMinnesota, United States2 53.327 June6.97.7×
TorontoOntario, Canada2 63.830 June8.47.6×
East Saint LouisIllinois, United States2 71.728 June9.67.5×
Saint PaulMinnesota, United States3 61.228 June8.27.5×
BridgeportConnecticut, United States3 60.030 June8.07.5×
ElizabethtownKentucky, United States2 55.828 June7.47.5×
PhiladelphiaPennsylvania, United States4 72.729 June9.97.3×
PennsaukenNew Jersey, United States3 70.529 June9.67.3×
St. LouisMissouri, United States2 74.228 June10.37.2×
Granite CityIllinois, United States1 65.128 June9.27.1×
Valley StationKentucky, United States3 61.428 June8.77.1×
TrentonNew Jersey, United States3 61.730 June8.96.9×
Winston-SalemNorth Carolina, United States3 60.529 June8.86.9×
South VinelandNew Jersey, United States2 51.529 June7.56.9×
SpringfieldMassachusetts, United States2 48.91 July7.16.9×
EdmundstonNew Brunswick, Canada1 46.425 June6.76.9×
KeeneNew Hampshire, United States2 45.41 July6.66.9×
WaterburyConnecticut, United States3 52.71 July7.76.8×
LindenNew Jersey, United States3 62.730 June9.36.7×
Fort LeeNew Jersey, United States3 52.530 June7.86.7×
BurlingtonVermont, United States4 61.725 June9.46.6×
New HavenConnecticut, United States3 51.030 June7.76.6×
EwingNew Jersey, United States3 64.130 June9.86.5×
New York CityNew York, United States3 57.430 June8.86.5×
ArnoldMissouri, United States1 46.628 June7.26.5×
Fall RiverMassachusetts, United States2 42.21 July6.56.5×
ProvidenceRhode Island, United States2 40.81 July6.36.5×
ElizabethNew Jersey, United States3 66.130 June10.36.4×
SuperiorWisconsin, United States2 48.727 June7.66.4×
HolbrookNew York, United States2 44.030 June6.96.4×
AlbanyNew York, United States3 54.31 July8.66.3×
ClemmonsNorth Carolina, United States3 49.429 June7.86.3×
East HamptonVirginia, United States4 45.729 June7.46.2×
Jersey CityNew Jersey, United States3 54.530 June9.16.0×
KnoxvilleTennessee, United States3 50.229 June8.46.0×
ChattanoogaTennessee, United States2 51.029 June8.85.8×
DanburyConnecticut, United States2 46.730 June8.15.8×
HempsteadNew York, United States2 45.130 June7.85.8×
KingsportTennessee, United States3 41.829 June7.35.7×
MonctonNew Brunswick, Canada1 28.625 June4.65.7×
GreensboroNorth Carolina, United States3 48.329 June8.65.6×
RaleighNorth Carolina, United States4 46.729 June8.45.6×
CoventryRhode Island, United States2 27.81 July5.05.6×
HartfordConnecticut, United States3 47.01 July8.55.5×
MaryvilleTennessee, United States2 44.329 June8.05.5×
Toms RiverNew Jersey, United States2 42.830 June8.05.4×
BrocktonMassachusetts, United States2 40.81 July7.65.4×
Sioux FallsSouth Dakota, United States1 27.027 June4.45.4×
CheektowagaNew York, United States3 76.128 June14.45.3×
MorrisvilleNorth Carolina, United States3 47.829 June9.05.3×
New LondonConnecticut, United States2 38.630 June7.35.3×
DurhamNorth Carolina, United States1 37.230 June7.05.3×
LexingtonNorth Carolina, United States2 44.929 June8.75.2×
QuincyMassachusetts, United States2 34.11 July6.65.2×
Roanoke RapidsNorth Carolina, United States3 48.029 June9.45.1×
TrussvilleAlabama, United States1 38.330 June7.55.1×
AberdeenSouth Dakota, United States1 25.327 June3.65.1×
CookevilleTennessee, United States2 36.628 June7.35.0×
West FargoNorth Dakota, United States1 30.827 June6.15.0×
East RidgeTennessee, United States2 47.729 June9.84.9×
GainesvilleGeorgia, United States2 44.829 June9.44.8×
LawrencevilleGeorgia, United States2 37.229 June7.84.8×
PleasantvilleNew Jersey, United States3 40.229 June8.54.7×
HickoryNorth Carolina, United States2 38.729 June8.44.6×
HueytownAlabama, United States1 35.830 June7.84.6×
BrookingsSouth Dakota, United States1 25.127 June5.54.6×
BostonMassachusetts, United States2 34.02 July7.54.5×
GreenvilleSouth Carolina, United States1 33.029 June7.44.5×
AshevilleNorth Carolina, United States2 32.329 June7.24.5×
WatertownSouth Dakota, United States1 27.327 June6.14.5×
CharlotteNorth Carolina, United States2 37.529 June8.64.4×
LowellMassachusetts, United States2 29.61 July6.84.4×
Candler-McAfeeGeorgia, United States2 38.030 June8.94.3×
ChesapeakeVirginia, United States3 34.529 June8.14.3×
PatersonNew Jersey, United States2 36.41 July8.74.2×
HendersonvilleTennessee, United States2 33.828 June8.34.1×
AtlantaGeorgia, United States2 34.029 June8.64.0×
GreenvilleNorth Carolina, United States3 33.41 July8.34.0×
LynnMassachusetts, United States1 26.42 July6.64.0×
FayettevilleNorth Carolina, United States2 34.329 June9.13.8×
FlorenceSouth Carolina, United States3 33.629 June9.03.7×
AugustaGeorgia, United States2 27.630 June7.63.6×
Warner RobinsGeorgia, United States1 28.730 June8.13.5×
MaconGeorgia, United States1 31.530 June9.43.4×
North CharlestonSouth Carolina, United States1 27.030 June7.93.4×
ClaytonNorth Carolina, United States2 29.830 June8.93.3×
Phenix CityAlabama, United States2 25.729 June7.73.3×
SpartanburgSouth Carolina, United States2 31.329 June9.93.2×
HernandoMississippi, United States1 25.028 June7.73.2×
Saint AndrewsSouth Carolina, United States3 28.01 July8.93.1×
PortlandMaine, United States1 25.22 July8.23.1×
BirminghamAlabama, United States2 28.830 June9.63.0×
GadsdenAlabama, United States1 25.830 June9.12.8×

Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.

Against other episodes in the United States and Canada

The largest of 141 episodes in the United States and Canada since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 141.

Use this page

SmogRank, Eastern United States and Canada, 25 June to 2 July 2023: 280 cities with PM2.5 at twice their usual or more, 25 June to 2 July 2023, smogrank.com/episodes/2023-06-25-eastern-united-states-and-canada (accessed 4 October 2026).

Download top 10 (PNG)

You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.