SmogRank / Episodes / United States

Northern United States and Canada, May 2023

For 5 days, from 15 to 19 May 2023, 83 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Grande Prairie, Alberta, Canada: 459.0 µg/m³ on 18 May, about 92× its usual 4.1. Ended 19 May.

Likely smoke from firesFires were detected within 300 km of the city on 34% of the counted city-days and smoke was mapped over the city on 95%. Satellites see crop, field and forest fires alike, so this doesn't say which burned.
Cities reached83in 2 countries
Days515 to 19 May 2023
Worst day18 May59 cities counted
Furthest above usual92×Grande Prairie

Day by day

18 May 59 cities at twice their usual or more
LanderIdaho FallsRock SpringsCondaLaramiePocatelloPrestonSmithfieldFort CollinsVernalBrandonNorth OgdenGreeleyRooseveltLongmontBoulderBountifulSalt Lake CityThorntonMillcreekWest JordanMagnaDenverCedar HillsHighlandKen CarylHerrimanOremStansbury parkTwin FallsTooeleSpanish ForkGrand JunctionSandpointCrestonDrayton ValleyCoeur d'AleneColorado SpringsMoscowLewistonGarden CitySpokane ValleyPullmanMeadMeridianSpokaneNampaCheneyAirway HeightsCastlegarLa GrandeWalla WallaPendletonSioux FallsFinleyPascoMoses LakeTri-CitiesHermistonEphrataQuincyProsserSunnysideWenatcheeToppenishYakimaEllensburgBeatriceBellevuePrinevilleThe DallesHopeMadrasRedmondHood RiverAgassizBendChilliwackEnumclawMarysvilleBellevueRentonAuburnKentSpanish SpringsTopekaAbbotsfordSeattleShorelineMount VernonWhite CenterRenoParklandTacomaLyndenBellinghamSaint JosephCarson CityAnacortesGreshamBremertonOak HarborMill PlainLangleyAnkenyOrchardsPort TownsendDes MoinesSalmon CreekTruckeePort CoquitlamVancouverMilwaukieAltamontCoquitlamLaceyPortlandNorth PortlandSouth Lake TahoeRidgefieldCanbyStrawberry HillDuluthSuperiorTigardBeavertonCentraliaBurnabyChehalisLongviewSilvertonOlatheDeltaKansas CityWoodburnWhistlerStaytonSheltonNorth VancouverSweet HomeKansas CityHillsboroVancouverKearneyRichmondLibertyWest VancouverSquamishForest GroveSalemVictoriaRaymoreMcMinnvillePort AngelesAlbanyLangfordEugeneGibsonsCottage GroveDallasWaterlooCorvallisNorth CowichanDuncanAshlandNorth AuburnEau ClaireTalentParadiseAberdeenYrekaAltoonaMedfordNanaimoLincolnHarewoodFolsomChicoRancho MurietaRosevilleGreenGridleyAndersonReddingYuba CityRed BluffArden-ArcadeGrants PassLa CrosseSacramentoGaltColusaWillowsStocktonMantecaDavisRio VistaTracyCoos BayPort AlberniVacavilleCourtenayConcordMuscatineBrookingsCrescent CitySan LeandroCampbell RiverRichmondOaklandUkiahSan RafaelSebastopolSan FranciscoDavenportMolineClintonRockfordPeoriaAppletonUniversity CityArnoldLemaySpringfieldSt. LouisGranite CityEast Saint LouisGreen BayBloomingtonGreendaleDecaturSouth MilwaukeeNapervilleBraidwoodWinthrop HarborZionJolietFranklin ParkOak LawnChicagoSavoyCalumet CityHammondEast ChicagoGaryPortageTerre HauteLafayetteHollandKitimatTerraceSouth BendHudsonvilleJenisonEvansvilleGrand RapidsElkhartKokomoKalamazooBloomingtonOwensboroIndianapolisFishersMcCordsvilleColumbia CityAndersonColumbusNew AlbanyValley StationLouisvilleJeffersonvilleSaint MatthewsJeffersontownMilwaukeeRexburgWaukeshaCaryDes PlainesIowa CityRochesterNorthbrookBarabooJerseyvilleBlaineCloquetMadisonGreat FallsGrand CentreOmahaSaint PaulRanchettesCheyenneVirginiaMissoulaLincolnPentictonCasperLockwoodBillingsCodyLewistownBozemanMinneapolisRivertonBrainerdSheridanBlairSaint MichaelButteBurnsvilleBrookingsMedicine HatApple ValleyHavreSmithersSaint CloudGrand IslandShakopeeSherwood ParkKelownaHelena Valley West CentralHelenaFort McMurrayGilletteVernonWatertownEdmontonFort SaskatchewanLethbridgeColumbia FallsSt. AlbertCranbrookWest FargoAberdeenQuesnelVermillionRapid CityMarshallDetroit LakesWilliams LakePrince GeorgeKamloopsCalgarySaskatoonRed DeerAirdrieScottsbluffEstevanSwift CurrentReginaEdsonFort St. JohnPierrePrince AlbertMiles CityGrande Prairie
12 May13141516171819202122
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

Grande PrairieGrande Prairie, 12 May: 26.4 µg/m³Grande Prairie, 13 May: 30.2 µg/m³Grande Prairie, 14 May: 70.3 µg/m³Grande Prairie, 15 May: 217.0 µg/m³, 43× its usual 4.1Grande Prairie, 16 May: 257.0 µg/m³, 51× its usual 4.1Grande Prairie, 17 May: 146.0 µg/m³, 29× its usual 4.1Grande Prairie, 18 May: 459.0 µg/m³, 92× its usual 4.1Grande Prairie, 19 May: 343.0 µg/m³Grande Prairie, 20 May: 306.0 µg/m³Grande Prairie, 21 May: 134.0 µg/m³Grande Prairie, 22 May: 76.7 µg/m³Fort St. JohnFort St. John, 12 May: 6.7 µg/m³Fort St. John, 13 May: 9.3 µg/m³Fort St. John, 14 May: 33.8 µg/m³Fort St. John, 15 May: 77.2 µg/m³, 15× its usual 5.1Fort St. John, 16 May: 45.0 µg/m³, 8.8× its usual 5.1Fort St. John, 17 May: 89.3 µg/m³, 17× its usual 5.2Fort St. John, 18 May: 167.0 µg/m³, 32× its usual 5.2Fort St. John, 19 May: 223.0 µg/m³Fort St. John, 20 May: 196.0 µg/m³Fort St. John, 21 May: 105.0 µg/m³Fort St. John, 22 May: 33.5 µg/m³EdsonEdson, 12 May: 12.4 µg/m³Edson, 13 May: 16.0 µg/m³Edson, 14 May: 20.6 µg/m³Edson, 15 May: 57.8 µg/m³, 11× its usual 5.1Edson, 16 May: 162.0 µg/m³, 32× its usual 5.1Edson, 17 May: 112.0 µg/m³, 22× its usual 5.2Edson, 18 May: 108.0 µg/m³, 20× its usual 5.3Edson, 19 May: 58.8 µg/m³Edson, 20 May: 186.0 µg/m³Edson, 21 May: 229.0 µg/m³Edson, 22 May: 42.8 µg/m³Prince GeorgePrince George, 12 May: 8.7 µg/m³Prince George, 13 May: 26.9 µg/m³Prince George, 14 May: 23.4 µg/m³Prince George, 15 May: 28.2 µg/m³, 5.6× its usual 4.7Prince George, 16 May: 95.4 µg/m³, 19× its usual 4.5Prince George, 17 May: 72.5 µg/m³, 15× its usual 4.5Prince George, 18 May: 81.6 µg/m³, 16× its usual 4.5Prince George, 19 May: 24.9 µg/m³Prince George, 20 May: 7.9 µg/m³Prince George, 21 May: 5.8 µg/m³Prince George, 22 May: 4.5 µg/m³Prince AlbertPrince Albert, 12 May: 13.3 µg/m³Prince Albert, 13 May: 20.5 µg/m³Prince Albert, 14 May: 29.3 µg/m³Prince Albert, 15 May: 15.5 µg/m³Prince Albert, 16 May: 227.0 µg/m³, 33× its usual 6.8Prince Albert, 17 May: 134.0 µg/m³, 20× its usual 6.8Prince Albert, 18 May: 11.7 µg/m³Prince Albert, 19 May: 20.3 µg/m³Prince Albert, 20 May: 101.0 µg/m³Prince Albert, 21 May: 16.3 µg/m³Prince Albert, 22 May: 38.2 µg/m³SaskatoonSaskatoon, 12 May: 7.5 µg/m³Saskatoon, 13 May: 21.5 µg/m³Saskatoon, 14 May: 16.3 µg/m³Saskatoon, 15 May: 11.8 µg/m³Saskatoon, 16 May: 97.9 µg/m³, 16× its usual 6.3Saskatoon, 17 May: 138.0 µg/m³, 22× its usual 6.3Saskatoon, 18 May: 15.6 µg/m³Saskatoon, 19 May: 15.3 µg/m³Saskatoon, 20 May: 105.0 µg/m³Saskatoon, 21 May: 23.3 µg/m³Saskatoon, 22 May: 38.4 µg/m³Red DeerRed Deer, 12 May: 8.4 µg/m³Red Deer, 13 May: 7.7 µg/m³Red Deer, 14 May: 7.7 µg/m³Red Deer, 15 May: 5.4 µg/m³Red Deer, 16 May: 134.5 µg/m³, 24× its usual 5.7Red Deer, 17 May: 129.5 µg/m³, 23× its usual 5.7Red Deer, 18 May: 15.0 µg/m³Red Deer, 19 May: 34.3 µg/m³Red Deer, 20 May: 191.0 µg/m³Red Deer, 21 May: 175.5 µg/m³Red Deer, 22 May: 110.8 µg/m³CalgaryCalgary, 12 May: 6.1 µg/m³Calgary, 13 May: 9.2 µg/m³Calgary, 14 May: 8.1 µg/m³Calgary, 15 May: 16.8 µg/m³Calgary, 16 May: 112.5 µg/m³, 18× its usual 6.3Calgary, 17 May: 130.5 µg/m³, 21× its usual 6.3Calgary, 18 May: 50.8 µg/m³, 8.1× its usual 6.3Calgary, 19 May: 25.6 µg/m³Calgary, 20 May: 98.0 µg/m³Calgary, 21 May: 47.9 µg/m³Calgary, 22 May: 52.8 µg/m³AirdrieAirdrie, 12 May: 5.9 µg/m³Airdrie, 13 May: 9.6 µg/m³Airdrie, 14 May: 6.2 µg/m³Airdrie, 15 May: 4.0 µg/m³Airdrie, 16 May: 111.0 µg/m³, 22× its usual 4.4Airdrie, 17 May: 130.0 µg/m³, 26× its usual 4.5Airdrie, 18 May: 31.2 µg/m³, 6.2× its usual 4.5Airdrie, 19 May: 47.4 µg/m³Airdrie, 20 May: 184.0 µg/m³Airdrie, 21 May: 89.1 µg/m³Airdrie, 22 May: 53.1 µg/m³QuesnelQuesnel, 12 May: 7.0 µg/m³Quesnel, 13 May: 11.5 µg/m³Quesnel, 14 May: 9.0 µg/m³Quesnel, 15 May: 13.8 µg/m³Quesnel, 16 May: 74.1 µg/m³, 13× its usual 5.7Quesnel, 17 May: 96.2 µg/m³, 17× its usual 5.8Quesnel, 18 May: 57.9 µg/m³, 10.0× its usual 5.8Quesnel, 19 May: no readingQuesnel, 20 May: no readingQuesnel, 21 May: no readingQuesnel, 22 May: no readingWilliams LakeWilliams Lake, 12 May: no readingWilliams Lake, 13 May: no readingWilliams Lake, 14 May: no readingWilliams Lake, 15 May: no readingWilliams Lake, 16 May: 43.3 µg/m³, 8.7× its usual 2.8Williams Lake, 17 May: 92.5 µg/m³, 19× its usual 2.8Williams Lake, 18 May: 43.5 µg/m³, 8.7× its usual 2.8Williams Lake, 19 May: 25.3 µg/m³Williams Lake, 20 May: 8.7 µg/m³Williams Lake, 21 May: 4.4 µg/m³Williams Lake, 22 May: 3.5 µg/m³EdmontonEdmonton, 12 May: 9.2 µg/m³Edmonton, 13 May: 8.3 µg/m³Edmonton, 14 May: 10.6 µg/m³Edmonton, 15 May: 8.3 µg/m³Edmonton, 16 May: 48.6 µg/m³, 7.0× its usual 6.9Edmonton, 17 May: 91.0 µg/m³, 13× its usual 6.9Edmonton, 18 May: 20.4 µg/m³Edmonton, 19 May: 102.0 µg/m³Edmonton, 20 May: 309.5 µg/m³Edmonton, 21 May: 273.0 µg/m³Edmonton, 22 May: 122.0 µg/m³Fort SaskatchewanFort Saskatchewan, 12 May: 9.8 µg/m³Fort Saskatchewan, 13 May: 8.3 µg/m³Fort Saskatchewan, 14 May: 10.7 µg/m³Fort Saskatchewan, 15 May: 7.3 µg/m³Fort Saskatchewan, 16 May: 46.5 µg/m³, 8.0× its usual 5.8Fort Saskatchewan, 17 May: 82.3 µg/m³, 14× its usual 5.9Fort Saskatchewan, 18 May: 20.2 µg/m³Fort Saskatchewan, 19 May: 108.0 µg/m³Fort Saskatchewan, 20 May: 325.0 µg/m³Fort Saskatchewan, 21 May: 314.0 µg/m³Fort Saskatchewan, 22 May: 105.0 µg/m³St. AlbertSt. Albert, 12 May: 6.5 µg/m³St. Albert, 13 May: 7.2 µg/m³St. Albert, 14 May: 10.1 µg/m³St. Albert, 15 May: 5.9 µg/m³St. Albert, 16 May: 44.4 µg/m³, 8.5× its usual 5.2St. Albert, 17 May: 77.6 µg/m³, 15× its usual 5.3St. Albert, 18 May: 14.8 µg/m³St. Albert, 19 May: 78.0 µg/m³St. Albert, 20 May: 231.0 µg/m³St. Albert, 21 May: 195.0 µg/m³St. Albert, 22 May: 84.7 µg/m³LethbridgeLethbridge, 12 May: 10.0 µg/m³Lethbridge, 13 May: 8.2 µg/m³Lethbridge, 14 May: 3.9 µg/m³Lethbridge, 15 May: 5.0 µg/m³Lethbridge, 16 May: 32.0 µg/m³, 6.4× its usual 4.1Lethbridge, 17 May: 71.8 µg/m³, 14× its usual 4.1Lethbridge, 18 May: 22.7 µg/m³Lethbridge, 19 May: 37.9 µg/m³Lethbridge, 20 May: 69.0 µg/m³Lethbridge, 21 May: 25.1 µg/m³Lethbridge, 22 May: 3.2 µg/m³Fort McMurrayFort McMurray, 12 May: 34.5 µg/m³Fort McMurray, 13 May: 70.8 µg/m³Fort McMurray, 14 May: 38.6 µg/m³Fort McMurray, 15 May: 15.0 µg/m³Fort McMurray, 16 May: 52.8 µg/m³, 11× its usual 4.8Fort McMurray, 17 May: 5.8 µg/m³Fort McMurray, 18 May: 8.0 µg/m³Fort McMurray, 19 May: 56.9 µg/m³Fort McMurray, 20 May: 92.2 µg/m³Fort McMurray, 21 May: 343.5 µg/m³Fort McMurray, 22 May: 140.5 µg/m³Sherwood ParkSherwood Park, 12 May: 9.4 µg/m³Sherwood Park, 13 May: 7.2 µg/m³Sherwood Park, 14 May: 7.8 µg/m³Sherwood Park, 15 May: 4.8 µg/m³Sherwood Park, 16 May: 30.8 µg/m³, 6.2× its usual 4.9Sherwood Park, 17 May: 50.8 µg/m³, 10× its usual 4.9Sherwood Park, 18 May: 11.1 µg/m³Sherwood Park, 19 May: 67.1 µg/m³Sherwood Park, 20 May: 204.0 µg/m³Sherwood Park, 21 May: 119.0 µg/m³Sherwood Park, 22 May: 53.8 µg/m³Great FallsGreat Falls, 12 May: 9.1 µg/m³Great Falls, 13 May: 10.5 µg/m³Great Falls, 14 May: 9.7 µg/m³Great Falls, 15 May: 9.2 µg/m³Great Falls, 16 May: 41.2 µg/m³, 5.2× its usual 7.9Great Falls, 17 May: 23.1 µg/m³Great Falls, 18 May: 31.3 µg/m³, 4.0× its usual 7.9Great Falls, 19 May: 41.2 µg/m³Great Falls, 20 May: 47.7 µg/m³Great Falls, 21 May: 32.2 µg/m³Great Falls, 22 May: 10.2 µg/m³EstevanEstevan, 12 May: 8.5 µg/m³Estevan, 13 May: 10.8 µg/m³Estevan, 14 May: 6.2 µg/m³Estevan, 15 May: 8.8 µg/m³Estevan, 16 May: 8.3 µg/m³Estevan, 17 May: 186.0 µg/m³, 29× its usual 6.4Estevan, 18 May: 20.2 µg/m³Estevan, 19 May: 17.8 µg/m³Estevan, 20 May: 25.0 µg/m³Estevan, 21 May: 16.3 µg/m³Estevan, 22 May: 23.5 µg/m³Miles CityMiles City, 12 May: 6.8 µg/m³Miles City, 13 May: 5.6 µg/m³Miles City, 14 May: 7.2 µg/m³Miles City, 15 May: 5.8 µg/m³Miles City, 16 May: 5.6 µg/m³Miles City, 17 May: 177.0 µg/m³, 34× its usual 5.2Miles City, 18 May: 73.9 µg/m³, 14× its usual 5.3Miles City, 19 May: 22.1 µg/m³Miles City, 20 May: 21.5 µg/m³Miles City, 21 May: 47.0 µg/m³Miles City, 22 May: 47.9 µg/m³PierrePierre, 12 May: 6.2 µg/m³Pierre, 13 May: 3.9 µg/m³Pierre, 14 May: 4.9 µg/m³Pierre, 15 May: 4.1 µg/m³Pierre, 16 May: 4.6 µg/m³Pierre, 17 May: 98.2 µg/m³, 20× its usual 3.5Pierre, 18 May: 162.0 µg/m³, 32× its usual 3.4Pierre, 19 May: 4.4 µg/m³Pierre, 20 May: 7.9 µg/m³Pierre, 21 May: 9.6 µg/m³Pierre, 22 May: 14.4 µg/m³ReginaRegina, 12 May: 7.7 µg/m³Regina, 13 May: 10.8 µg/m³Regina, 14 May: 10.7 µg/m³Regina, 15 May: 9.9 µg/m³Regina, 16 May: 18.4 µg/m³Regina, 17 May: 160.0 µg/m³, 30× its usual 5.3Regina, 18 May: 12.3 µg/m³Regina, 19 May: 14.5 µg/m³Regina, 20 May: 29.4 µg/m³Regina, 21 May: 17.1 µg/m³Regina, 22 May: 27.2 µg/m³Swift CurrentSwift Current, 12 May: 6.7 µg/m³Swift Current, 13 May: 13.1 µg/m³Swift Current, 14 May: 10.0 µg/m³Swift Current, 15 May: 9.1 µg/m³Swift Current, 16 May: 24.8 µg/m³Swift Current, 17 May: 151.0 µg/m³, 30× its usual 4.9Swift Current, 18 May: 27.0 µg/m³Swift Current, 19 May: 19.3 µg/m³Swift Current, 20 May: 154.0 µg/m³Swift Current, 21 May: 82.0 µg/m³Swift Current, 22 May: 40.1 µg/m³KamloopsKamloops, 12 May: 7.3 µg/m³Kamloops, 13 May: 9.8 µg/m³Kamloops, 14 May: 10.5 µg/m³Kamloops, 15 May: 7.7 µg/m³Kamloops, 16 May: 9.4 µg/m³Kamloops, 17 May: 99.5 µg/m³, 20× its usual 4.6Kamloops, 18 May: 79.7 µg/m³, 16× its usual 4.6Kamloops, 19 May: 8.2 µg/m³Kamloops, 20 May: 7.9 µg/m³Kamloops, 21 May: 5.3 µg/m³Kamloops, 22 May: 3.1 µg/m³West FargoWest Fargo, 12 May: 14.3 µg/m³West Fargo, 13 May: 12.4 µg/m³West Fargo, 14 May: 10.6 µg/m³West Fargo, 15 May: 11.0 µg/m³West Fargo, 16 May: 27.1 µg/m³West Fargo, 17 May: 40.7 µg/m³, 6.8× its usual 6.0West Fargo, 18 May: 99.0 µg/m³, 17× its usual 6.0West Fargo, 19 May: 4.3 µg/m³West Fargo, 20 May: 10.9 µg/m³West Fargo, 21 May: 16.3 µg/m³West Fargo, 22 May: 20.6 µg/m³Rapid CityRapid City, 12 May: 2.9 µg/m³Rapid City, 13 May: 3.3 µg/m³Rapid City, 14 May: 8.1 µg/m³Rapid City, 15 May: 6.4 µg/m³Rapid City, 16 May: 6.0 µg/m³Rapid City, 17 May: 34.9 µg/m³, 6.8× its usual 5.1Rapid City, 18 May: 90.2 µg/m³, 17× its usual 5.2Rapid City, 19 May: 24.6 µg/m³Rapid City, 20 May: 23.1 µg/m³Rapid City, 21 May: 24.8 µg/m³Rapid City, 22 May: 30.9 µg/m³AberdeenAberdeen, 12 May: 4.8 µg/m³Aberdeen, 13 May: 6.8 µg/m³Aberdeen, 14 May: 4.6 µg/m³Aberdeen, 15 May: 3.4 µg/m³Aberdeen, 16 May: 4.6 µg/m³Aberdeen, 17 May: 46.0 µg/m³, 9.2× its usual 3.8Aberdeen, 18 May: 82.8 µg/m³, 17× its usual 3.8Aberdeen, 19 May: 3.3 µg/m³Aberdeen, 20 May: 5.0 µg/m³Aberdeen, 21 May: 7.9 µg/m³Aberdeen, 22 May: 16.2 µg/m³CranbrookCranbrook, 12 May: 6.5 µg/m³Cranbrook, 13 May: 6.8 µg/m³Cranbrook, 14 May: 5.6 µg/m³Cranbrook, 15 May: 3.8 µg/m³Cranbrook, 16 May: 5.6 µg/m³Cranbrook, 17 May: 52.1 µg/m³, 10× its usual 4.5Cranbrook, 18 May: 75.6 µg/m³, 15× its usual 4.5Cranbrook, 19 May: 22.7 µg/m³Cranbrook, 20 May: 11.0 µg/m³Cranbrook, 21 May: 4.9 µg/m³Cranbrook, 22 May: 3.2 µg/m³Columbia FallsColumbia Falls, 12 May: 6.7 µg/m³Columbia Falls, 13 May: 6.9 µg/m³Columbia Falls, 14 May: 5.4 µg/m³Columbia Falls, 15 May: 4.7 µg/m³Columbia Falls, 16 May: 18.5 µg/m³Columbia Falls, 17 May: 73.8 µg/m³, 14× its usual 5.1Columbia Falls, 18 May: 67.7 µg/m³, 14× its usual 5.0Columbia Falls, 19 May: 49.4 µg/m³Columbia Falls, 20 May: 23.2 µg/m³Columbia Falls, 21 May: 13.6 µg/m³Columbia Falls, 22 May: 5.0 µg/m³HelenaHelena, 12 May: 4.9 µg/m³Helena, 13 May: 4.3 µg/m³Helena, 14 May: 4.6 µg/m³Helena, 15 May: 4.7 µg/m³Helena, 16 May: 13.7 µg/m³Helena, 17 May: 30.0 µg/m³, 4.3× its usual 7.0Helena, 18 May: 72.5 µg/m³, 10× its usual 7.0Helena, 19 May: 73.8 µg/m³Helena, 20 May: 34.8 µg/m³Helena, 21 May: 19.9 µg/m³Helena, 22 May: 5.1 µg/m³Helena Valley West …Helena Valley West Central, 12 May: 4.9 µg/m³Helena Valley West Central, 13 May: 4.3 µg/m³Helena Valley West Central, 14 May: 4.6 µg/m³Helena Valley West Central, 15 May: 4.7 µg/m³Helena Valley West Central, 16 May: 13.7 µg/m³Helena Valley West Central, 17 May: 30.0 µg/m³, 4.3× its usual 7.0Helena Valley West Central, 18 May: 72.5 µg/m³, 10× its usual 7.0Helena Valley West Central, 19 May: 73.8 µg/m³Helena Valley West Central, 20 May: 34.8 µg/m³Helena Valley West Central, 21 May: 19.9 µg/m³Helena Valley West Central, 22 May: 5.1 µg/m³VernonVernon, 12 May: 6.1 µg/m³Vernon, 13 May: 5.9 µg/m³Vernon, 14 May: 6.2 µg/m³Vernon, 15 May: 7.0 µg/m³Vernon, 16 May: 6.4 µg/m³Vernon, 17 May: 48.9 µg/m³, 9.8× its usual 4.9Vernon, 18 May: 60.7 µg/m³, 12× its usual 4.8Vernon, 19 May: 9.3 µg/m³Vernon, 20 May: 7.1 µg/m³Vernon, 21 May: 3.8 µg/m³Vernon, 22 May: 1.3 µg/m³KelownaKelowna, 12 May: 5.4 µg/m³Kelowna, 13 May: 6.7 µg/m³Kelowna, 14 May: 8.9 µg/m³Kelowna, 15 May: 7.4 µg/m³Kelowna, 16 May: 5.1 µg/m³Kelowna, 17 May: 39.5 µg/m³, 7.9× its usual 3.8Kelowna, 18 May: 52.1 µg/m³, 10× its usual 3.8Kelowna, 19 May: 12.2 µg/m³Kelowna, 20 May: 8.6 µg/m³Kelowna, 21 May: 5.5 µg/m³Kelowna, 22 May: 1.6 µg/m³HavreHavre, 12 May: 3.0 µg/m³Havre, 13 May: 5.2 µg/m³Havre, 14 May: 7.5 µg/m³Havre, 15 May: 4.8 µg/m³Havre, 16 May: 5.6 µg/m³Havre, 17 May: 47.5 µg/m³, 9.5× its usual 3.1Havre, 18 May: 24.6 µg/m³Havre, 19 May: 25.6 µg/m³Havre, 20 May: 61.3 µg/m³Havre, 21 May: 131.0 µg/m³Havre, 22 May: 40.0 µg/m³Medicine HatMedicine Hat, 12 May: 3.7 µg/m³Medicine Hat, 13 May: 5.2 µg/m³Medicine Hat, 14 May: 5.4 µg/m³Medicine Hat, 15 May: 4.7 µg/m³Medicine Hat, 16 May: 11.3 µg/m³Medicine Hat, 17 May: 46.8 µg/m³, 9.4× its usual 4.1Medicine Hat, 18 May: 15.2 µg/m³Medicine Hat, 19 May: 28.7 µg/m³Medicine Hat, 20 May: 104.0 µg/m³Medicine Hat, 21 May: 74.7 µg/m³Medicine Hat, 22 May: 19.6 µg/m³LewistownLewistown, 12 May: 4.7 µg/m³Lewistown, 13 May: 5.3 µg/m³Lewistown, 14 May: 3.4 µg/m³Lewistown, 15 May: 3.9 µg/m³Lewistown, 16 May: 8.7 µg/m³Lewistown, 17 May: 33.6 µg/m³, 6.7× its usual 4.2Lewistown, 18 May: 34.5 µg/m³, 6.9× its usual 4.2Lewistown, 19 May: 15.0 µg/m³Lewistown, 20 May: 36.2 µg/m³Lewistown, 21 May: 34.2 µg/m³Lewistown, 22 May: 14.0 µg/m³BozemanBozeman, 12 May: 3.8 µg/m³Bozeman, 13 May: 3.3 µg/m³Bozeman, 14 May: 1.4 µg/m³Bozeman, 15 May: 3.3 µg/m³Bozeman, 16 May: 4.5 µg/m³Bozeman, 17 May: 26.5 µg/m³, 5.3× its usual 4.7Bozeman, 18 May: 34.5 µg/m³, 6.9× its usual 4.7Bozeman, 19 May: 31.6 µg/m³Bozeman, 20 May: 24.2 µg/m³Bozeman, 21 May: 15.7 µg/m³Bozeman, 22 May: 8.3 µg/m³BillingsBillings, 12 May: 5.2 µg/m³Billings, 13 May: 5.3 µg/m³Billings, 14 May: 4.6 µg/m³Billings, 15 May: 7.5 µg/m³Billings, 16 May: 3.0 µg/m³Billings, 17 May: 30.4 µg/m³, 6.1× its usual 3.7Billings, 18 May: 33.6 µg/m³, 6.7× its usual 3.7Billings, 19 May: 23.5 µg/m³Billings, 20 May: 24.8 µg/m³Billings, 21 May: 27.4 µg/m³Billings, 22 May: 12.2 µg/m³LockwoodLockwood, 12 May: 5.2 µg/m³Lockwood, 13 May: 5.3 µg/m³Lockwood, 14 May: 4.6 µg/m³Lockwood, 15 May: 7.5 µg/m³Lockwood, 16 May: 3.0 µg/m³Lockwood, 17 May: 30.4 µg/m³, 6.1× its usual 3.7Lockwood, 18 May: 33.6 µg/m³, 6.7× its usual 3.7Lockwood, 19 May: 23.5 µg/m³Lockwood, 20 May: 24.8 µg/m³Lockwood, 21 May: 27.4 µg/m³Lockwood, 22 May: 12.2 µg/m³ScottsbluffScottsbluff, 12 May: 1.1 µg/m³Scottsbluff, 13 May: 1.3 µg/m³Scottsbluff, 14 May: 2.1 µg/m³Scottsbluff, 15 May: 3.6 µg/m³Scottsbluff, 16 May: 1.3 µg/m³Scottsbluff, 17 May: 3.6 µg/m³Scottsbluff, 18 May: 144.0 µg/m³, 29× its usual 3.6Scottsbluff, 19 May: 32.2 µg/m³Scottsbluff, 20 May: 26.4 µg/m³Scottsbluff, 21 May: 17.7 µg/m³Scottsbluff, 22 May: 20.1 µg/m³Detroit LakesDetroit Lakes, 12 May: 7.1 µg/m³Detroit Lakes, 13 May: 7.3 µg/m³Detroit Lakes, 14 May: 5.8 µg/m³Detroit Lakes, 15 May: 6.8 µg/m³Detroit Lakes, 16 May: 12.8 µg/m³Detroit Lakes, 17 May: 13.3 µg/m³Detroit Lakes, 18 May: 89.2 µg/m³, 18× its usual 5.0Detroit Lakes, 19 May: 2.7 µg/m³Detroit Lakes, 20 May: 8.0 µg/m³Detroit Lakes, 21 May: 11.6 µg/m³Detroit Lakes, 22 May: 16.3 µg/m³MarshallMarshall, 12 May: 6.7 µg/m³Marshall, 13 May: 9.1 µg/m³Marshall, 14 May: 7.1 µg/m³Marshall, 15 May: 6.0 µg/m³Marshall, 16 May: 9.3 µg/m³Marshall, 17 May: 17.0 µg/m³Marshall, 18 May: 87.2 µg/m³, 17× its usual 4.9Marshall, 19 May: 7.1 µg/m³Marshall, 20 May: 16.3 µg/m³Marshall, 21 May: 20.2 µg/m³Marshall, 22 May: 16.0 µg/m³VermillionVermillion, 12 May: 5.6 µg/m³Vermillion, 13 May: 4.7 µg/m³Vermillion, 14 May: 4.4 µg/m³Vermillion, 15 May: 4.7 µg/m³Vermillion, 16 May: 5.5 µg/m³Vermillion, 17 May: 6.9 µg/m³Vermillion, 18 May: 85.7 µg/m³, 17× its usual 4.5Vermillion, 19 May: 7.2 µg/m³Vermillion, 20 May: 8.6 µg/m³Vermillion, 21 May: 11.2 µg/m³Vermillion, 22 May: 11.4 µg/m³WatertownWatertown, 12 May: 7.6 µg/m³Watertown, 13 May: 10.8 µg/m³Watertown, 14 May: 7.2 µg/m³Watertown, 15 May: 7.1 µg/m³Watertown, 16 May: 10.7 µg/m³Watertown, 17 May: 11.2 µg/m³Watertown, 18 May: 82.8 µg/m³, 13× its usual 6.6Watertown, 19 May: 6.0 µg/m³Watertown, 20 May: 12.7 µg/m³Watertown, 21 May: 22.2 µg/m³Watertown, 22 May: 18.3 µg/m³BrookingsBrookings, 12 May: 5.0 µg/m³Brookings, 13 May: 5.7 µg/m³Brookings, 14 May: 4.0 µg/m³Brookings, 15 May: 4.2 µg/m³Brookings, 16 May: 6.4 µg/m³Brookings, 17 May: 7.6 µg/m³Brookings, 18 May: 63.8 µg/m³, 9.1× its usual 7.0Brookings, 19 May: 2.9 µg/m³Brookings, 20 May: 8.6 µg/m³Brookings, 21 May: 16.8 µg/m³Brookings, 22 May: 9.5 µg/m³ShakopeeShakopee, 12 May: 10.2 µg/m³Shakopee, 13 May: 10.0 µg/m³Shakopee, 14 May: 8.0 µg/m³Shakopee, 15 May: 7.0 µg/m³Shakopee, 16 May: 11.1 µg/m³Shakopee, 17 May: 9.1 µg/m³Shakopee, 18 May: 59.0 µg/m³, 9.8× its usual 6.0Shakopee, 19 May: 8.0 µg/m³Shakopee, 20 May: 11.2 µg/m³Shakopee, 21 May: 23.0 µg/m³Shakopee, 22 May: 18.6 µg/m³GilletteGillette, 12 May: 3.5 µg/m³Gillette, 13 May: 2.3 µg/m³Gillette, 14 May: 3.9 µg/m³Gillette, 15 May: 6.2 µg/m³Gillette, 16 May: 4.6 µg/m³Gillette, 17 May: no readingGillette, 18 May: 55.1 µg/m³, 11× its usual 3.6Gillette, 19 May: 23.5 µg/m³Gillette, 20 May: 21.3 µg/m³Gillette, 21 May: 49.0 µg/m³Gillette, 22 May: 44.7 µg/m³BurnsvilleBurnsville, 12 May: 10.6 µg/m³Burnsville, 13 May: 9.5 µg/m³Burnsville, 14 May: 8.6 µg/m³Burnsville, 15 May: 8.2 µg/m³Burnsville, 16 May: 11.7 µg/m³Burnsville, 17 May: 8.7 µg/m³Burnsville, 18 May: 50.1 µg/m³, 8.9× its usual 5.6Burnsville, 19 May: 10.0 µg/m³Burnsville, 20 May: 12.3 µg/m³Burnsville, 21 May: 26.1 µg/m³Burnsville, 22 May: 20.5 µg/m³Apple ValleyApple Valley, 12 May: 9.4 µg/m³Apple Valley, 13 May: 9.3 µg/m³Apple Valley, 14 May: 8.0 µg/m³Apple Valley, 15 May: 7.6 µg/m³Apple Valley, 16 May: 10.8 µg/m³Apple Valley, 17 May: 8.4 µg/m³Apple Valley, 18 May: 49.9 µg/m³, 9.4× its usual 5.3Apple Valley, 19 May: 9.0 µg/m³Apple Valley, 20 May: 10.9 µg/m³Apple Valley, 21 May: 17.9 µg/m³Apple Valley, 22 May: 18.7 µg/m³Grand IslandGrand Island, 12 May: 5.7 µg/m³Grand Island, 13 May: 4.2 µg/m³Grand Island, 14 May: 3.6 µg/m³Grand Island, 15 May: 4.6 µg/m³Grand Island, 16 May: 5.1 µg/m³Grand Island, 17 May: 5.0 µg/m³Grand Island, 18 May: 49.2 µg/m³, 9.8× its usual 5.0Grand Island, 19 May: 24.8 µg/m³Grand Island, 20 May: no readingGrand Island, 21 May: 11.5 µg/m³Grand Island, 22 May: 10.0 µg/m³Saint CloudSaint Cloud, 12 May: 9.2 µg/m³Saint Cloud, 13 May: 8.0 µg/m³Saint Cloud, 14 May: 7.2 µg/m³Saint Cloud, 15 May: 7.2 µg/m³Saint Cloud, 16 May: 14.1 µg/m³Saint Cloud, 17 May: 7.7 µg/m³Saint Cloud, 18 May: 48.4 µg/m³, 9.7× its usual 4.8Saint Cloud, 19 May: 6.9 µg/m³Saint Cloud, 20 May: 9.0 µg/m³Saint Cloud, 21 May: 18.4 µg/m³Saint Cloud, 22 May: 16.5 µg/m³SmithersSmithers, 12 May: 5.9 µg/m³Smithers, 13 May: 7.7 µg/m³Smithers, 14 May: 6.7 µg/m³Smithers, 15 May: 7.4 µg/m³Smithers, 16 May: 12.0 µg/m³Smithers, 17 May: 8.1 µg/m³Smithers, 18 May: 48.3 µg/m³, 9.7× its usual 3.4Smithers, 19 May: 13.0 µg/m³Smithers, 20 May: 2.2 µg/m³Smithers, 21 May: no readingSmithers, 22 May: 1.5 µg/m³ButteButte, 12 May: 4.2 µg/m³Butte, 13 May: 3.1 µg/m³Butte, 14 May: no readingButte, 15 May: 2.9 µg/m³Butte, 16 May: 4.1 µg/m³Butte, 17 May: 17.6 µg/m³Butte, 18 May: 42.1 µg/m³, 8.4× its usual 3.9Butte, 19 May: 46.4 µg/m³Butte, 20 May: 22.1 µg/m³Butte, 21 May: 11.4 µg/m³Butte, 22 May: 3.9 µg/m³Saint MichaelSaint Michael, 12 May: 9.8 µg/m³Saint Michael, 13 May: no readingSaint Michael, 14 May: no readingSaint Michael, 15 May: 7.0 µg/m³Saint Michael, 16 May: 12.1 µg/m³Saint Michael, 17 May: 7.9 µg/m³Saint Michael, 18 May: 40.7 µg/m³, 8.1× its usual 5.0Saint Michael, 19 May: 6.6 µg/m³Saint Michael, 20 May: 9.5 µg/m³Saint Michael, 21 May: 16.7 µg/m³Saint Michael, 22 May: 17.5 µg/m³BlairBlair, 12 May: 5.5 µg/m³Blair, 13 May: 3.8 µg/m³Blair, 14 May: 7.9 µg/m³Blair, 15 May: 3.8 µg/m³Blair, 16 May: 3.0 µg/m³Blair, 17 May: 7.2 µg/m³Blair, 18 May: 40.2 µg/m³, 8.0× its usual 4.2Blair, 19 May: 12.5 µg/m³Blair, 20 May: 6.7 µg/m³Blair, 21 May: 8.7 µg/m³Blair, 22 May: 10.7 µg/m³SheridanSheridan, 12 May: 6.7 µg/m³Sheridan, 13 May: 6.3 µg/m³Sheridan, 14 May: 6.2 µg/m³Sheridan, 15 May: 5.7 µg/m³Sheridan, 16 May: 7.3 µg/m³Sheridan, 17 May: 24.8 µg/m³Sheridan, 18 May: 38.8 µg/m³, 7.8× its usual 3.7Sheridan, 19 May: 24.1 µg/m³Sheridan, 20 May: 21.8 µg/m³Sheridan, 21 May: 40.3 µg/m³Sheridan, 22 May: 31.4 µg/m³MinneapolisMinneapolis, 12 May: 9.7 µg/m³Minneapolis, 13 May: 9.7 µg/m³Minneapolis, 14 May: 8.2 µg/m³Minneapolis, 15 May: 8.8 µg/m³Minneapolis, 16 May: 11.6 µg/m³Minneapolis, 17 May: 8.0 µg/m³Minneapolis, 18 May: 38.5 µg/m³, 6.9× its usual 5.6Minneapolis, 19 May: 8.4 µg/m³Minneapolis, 20 May: 9.8 µg/m³Minneapolis, 21 May: 24.9 µg/m³Minneapolis, 22 May: 21.2 µg/m³BrainerdBrainerd, 12 May: 6.7 µg/m³Brainerd, 13 May: 6.8 µg/m³Brainerd, 14 May: 5.3 µg/m³Brainerd, 15 May: 6.4 µg/m³Brainerd, 16 May: 11.5 µg/m³Brainerd, 17 May: 6.1 µg/m³Brainerd, 18 May: 37.9 µg/m³, 7.6× its usual 4.0Brainerd, 19 May: 2.7 µg/m³Brainerd, 20 May: 6.9 µg/m³Brainerd, 21 May: 13.8 µg/m³Brainerd, 22 May: 11.5 µg/m³RivertonRiverton, 12 May: 3.1 µg/m³Riverton, 13 May: 3.1 µg/m³Riverton, 14 May: 1.7 µg/m³Riverton, 15 May: 2.3 µg/m³Riverton, 16 May: 3.2 µg/m³Riverton, 17 May: 6.9 µg/m³Riverton, 18 May: 37.3 µg/m³, 7.5× its usual 2.7Riverton, 19 May: 35.7 µg/m³Riverton, 20 May: 18.2 µg/m³Riverton, 21 May: 12.3 µg/m³Riverton, 22 May: 10.1 µg/m³CodyCody, 12 May: 3.7 µg/m³Cody, 13 May: 2.0 µg/m³Cody, 14 May: 1.8 µg/m³Cody, 15 May: 2.0 µg/m³Cody, 16 May: 3.6 µg/m³Cody, 17 May: 12.7 µg/m³Cody, 18 May: 34.2 µg/m³, 6.8× its usual 2.8Cody, 19 May: 30.2 µg/m³Cody, 20 May: 17.5 µg/m³Cody, 21 May: 11.5 µg/m³Cody, 22 May: 10.6 µg/m³12 May1416182022
The 60 cities with the highest readings of 83, 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
Grande PrairieAlberta, Canada4 459.018 May4.192×
Miles CityMontana, United States2 177.017 May5.234×
Prince AlbertSaskatchewan, Canada2 227.016 May6.833×
PierreSouth Dakota, United States2 162.018 May3.432×
Fort St. JohnBritish Columbia, Canada4 167.018 May5.232×
EdsonAlberta, Canada4 162.016 May5.132×
ReginaSaskatchewan, Canada1 160.017 May5.330×
Swift CurrentSaskatchewan, Canada1 151.017 May4.930×
EstevanSaskatchewan, Canada1 186.017 May6.429×
ScottsbluffNebraska, United States1 144.018 May3.629×
AirdrieAlberta, Canada3 130.017 May4.526×
Red DeerAlberta, Canada2 134.516 May5.724×
SaskatoonSaskatchewan, Canada2 138.017 May6.322×
CalgaryAlberta, Canada3 130.517 May6.321×
KamloopsBritish Columbia, Canada2 99.517 May4.620×
Prince GeorgeBritish Columbia, Canada4 95.416 May4.519×
Williams LakeBritish Columbia, Canada3 92.517 May2.819×
Detroit LakesMinnesota, United States1 89.218 May5.018×
MarshallMinnesota, United States1 87.218 May4.917×
Rapid CitySouth Dakota, United States2 90.218 May5.217×
VermillionSouth Dakota, United States1 85.718 May4.517×
QuesnelBritish Columbia, Canada3 96.217 May5.817×
AberdeenSouth Dakota, United States2 82.818 May3.817×
West FargoNorth Dakota, United States2 99.018 May6.017×
CranbrookBritish Columbia, Canada2 75.618 May4.515×
St. AlbertAlberta, Canada2 77.617 May5.315×
Columbia FallsMontana, United States2 73.817 May5.115×
LethbridgeAlberta, Canada2 71.817 May4.114×
Fort SaskatchewanAlberta, Canada2 82.317 May5.914×
EdmontonAlberta, Canada2 91.017 May6.913×
WatertownSouth Dakota, United States1 82.818 May6.613×
VernonBritish Columbia, Canada2 60.718 May4.812×
GilletteWyoming, United States1 55.118 May3.611×
Fort McMurrayAlberta, Canada1 52.816 May4.811×
HelenaMontana, United States2 72.518 May7.010×
Helena Valley West CentralMontana, United States2 72.518 May7.010×
KelownaBritish Columbia, Canada2 52.118 May3.810×
Sherwood ParkAlberta, Canada2 50.817 May4.910×
ShakopeeMinnesota, United States1 59.018 May6.09.8×
Grand IslandNebraska, United States1 49.218 May5.09.8×
Saint CloudMinnesota, United States1 48.418 May4.89.7×
SmithersBritish Columbia, Canada1 48.318 May3.49.7×
HavreMontana, United States1 47.517 May3.19.5×
Apple ValleyMinnesota, United States1 49.918 May5.39.4×
Medicine HatAlberta, Canada1 46.817 May4.19.4×
BrookingsSouth Dakota, United States1 63.818 May7.09.1×
BurnsvilleMinnesota, United States1 50.118 May5.68.9×
ButteMontana, United States1 42.118 May3.98.4×
Saint MichaelMinnesota, United States1 40.718 May5.08.1×
BlairNebraska, United States1 40.218 May4.28.0×
SheridanWyoming, United States1 38.818 May3.77.8×
BrainerdMinnesota, United States1 37.918 May4.07.6×
RivertonWyoming, United States1 37.318 May2.77.5×
MinneapolisMinnesota, United States1 38.518 May5.66.9×
BozemanMontana, United States2 34.518 May4.76.9×
LewistownMontana, United States2 34.518 May4.26.9×
CodyWyoming, United States1 34.218 May2.86.8×
BillingsMontana, United States2 33.618 May3.76.7×
LockwoodMontana, United States2 33.618 May3.76.7×
CasperWyoming, United States1 32.718 May2.56.5×
PentictonBritish Columbia, Canada2 29.517 May3.05.9×
LincolnNebraska, United States1 29.318 May4.85.9×
MissoulaMontana, United States1 29.218 May2.65.8×
VirginiaMinnesota, United States1 29.018 May3.85.8×
CheyenneWyoming, United States1 29.018 May3.05.8×
RanchettesWyoming, United States1 29.018 May3.05.8×
Saint PaulMinnesota, United States1 32.818 May5.95.6×
OmahaNebraska, United States1 31.218 May5.75.5×
Grand CentreAlberta, Canada1 27.216 May4.55.4×
Great FallsMontana, United States2 41.216 May7.95.2×
MadisonWisconsin, United States1 25.519 May5.05.1×
CloquetMinnesota, United States1 25.318 May3.35.1×
BlaineMinnesota, United States1 25.218 May4.85.0×
JerseyvilleIllinois, United States1 25.119 May4.85.0×
BarabooWisconsin, United States1 25.119 May4.05.0×
NorthbrookIllinois, United States1 27.619 May5.64.9×
RochesterMinnesota, United States1 28.018 May6.14.6×
Iowa CityIowa, United States1 26.719 May5.84.6×
Des PlainesIllinois, United States1 26.219 May5.84.5×
CaryIllinois, United States1 25.719 May5.84.4×
WaukeshaWisconsin, United States1 25.019 May5.94.2×
RexburgIdaho, United States1 25.818 May6.34.1×
MilwaukeeWisconsin, United States1 25.319 May6.53.9×

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

Number 18 of 173 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 173.

Use this page

SmogRank, Northern United States and Canada, May 2023: 83 cities with PM2.5 at twice their usual or more, 15 to 19 May 2023, smogrank.com/episodes/2023-05-northern-united-states-and-canada (accessed 5 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. Fire detections from NASA FIRMS; smoke maps from NOAA HMS.