SmogRank / Episodes / United States

North-western United States and Canada, 4 to 11 September 2024

For 8 days, from 4 to 11 September 2024, 63 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Prineville, Oregon, United States: 87.0 µg/m³ on 5 September, about 17× its usual 5.2. Ended 11 September.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached63in 2 countries
Days84 to 11 September 2024
Worst day8 September21 cities counted
Furthest above usual17×Prineville

Day by day

8 September 21 cities at twice their usual or more
RexburgIdaho FallsOntarioCondaGreat FallsCoeur d'AleneSandpointSpokane ValleyMeadAirway HeightsWalla WallaLethbridgeCrestonCranbrookCodyHighlandCedar HillsTri-CitiesLanderCastlegarMoses LakeRock SpringsWorlandEphrataRooseveltQuincyVernalWenatcheeEllensburgSheridanPentictonKelownaVernonHood RiverCasperSpanish SpringsSwift CurrentRenoAltamontGilletteKamloopsTruckeeGreshamAuburnRentonBellevueHopeSalmon CreekParklandMarysvilleWhite CenterSeattleTacomaNorth PortlandPicnic Point-North LynnwoodShorelineSweet HomeRidgefieldStaytonAgassizWoodburnChilliwackMount VernonBremertonLongviewHillsboroLaramieLaceySalemCentraliaChehalisAlbanyForest GroveAbbotsfordMcMinnvilleOak HarborMissionBellinghamYrekaAnacortesPort TownsendParadiseCorvallisLyndenDallasSheltonChicoReddingRoseburgLangleyGreenGridleyRed BluffGrants PassPort CoquitlamCoquitlamStrawberry HillRanchettesFort CollinsCheyenneBurnabyWillowsDeltaBoulderPort AngelesVictoriaLongmontAberdeenNorth VancouverRichmondVancouverLangfordWest VancouverArvadaGreeleyNorthglennLakewoodThorntonSquamishWhistlerKen CarylDenverBrightonLittletonCoos BayDuncanNorth CowichanGibsonsRapid CityReginaBrookingsCrescent CityHarewoodNanaimoSunnysideColumbia FallsMedicine HatBurleyProsserSpokaneToppenishWeiserYakimaMedfordVancouverLa GrandeBaker CityLockwoodBillingsPrestonEugeneMillcreekSilvertonPortlandTalentAshlandBountifulTigardLewistonCottage GroveSpanish ForkHermistonSmithfieldWest Valley CityWest JordanMilwaukieCanbyNorth OgdenPullmanBeavertonOremSalt Lake CityMoscowMagnaPendletonThe DallesBozemanNampaPocatelloMiles CityHerrimanRedmondGlendiveTooeleStansbury parkMadrasHavreTwin FallsHelena Valley West CentralHelenaLewistownGarden CityMissoulaBendMeridianButtePrineville
1 Sep234567891011121314
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

MeridianMeridian, 1 September: 47.0 µg/m³Meridian, 2 September: 15.6 µg/m³Meridian, 3 September: 26.2 µg/m³Meridian, 4 September: 38.4 µg/m³, 6.2× its usual 6.2Meridian, 5 September: 84.8 µg/m³, 14× its usual 6.2Meridian, 6 September: 31.4 µg/m³, 5.1× its usual 6.2Meridian, 7 September: 23.6 µg/m³Meridian, 8 September: 14.1 µg/m³Meridian, 9 September: 17.6 µg/m³Meridian, 10 September: 27.5 µg/m³, 4.6× its usual 6.0Meridian, 11 September: 17.7 µg/m³Meridian, 12 September: 7.7 µg/m³Meridian, 13 September: 6.6 µg/m³Meridian, 14 September: 6.0 µg/m³Garden CityGarden City, 1 September: 48.6 µg/m³Garden City, 2 September: 14.8 µg/m³Garden City, 3 September: 26.2 µg/m³Garden City, 4 September: 36.0 µg/m³, 6.9× its usual 5.2Garden City, 5 September: 53.5 µg/m³, 10× its usual 5.1Garden City, 6 September: 26.2 µg/m³, 5.1× its usual 5.1Garden City, 7 September: 18.8 µg/m³Garden City, 8 September: 11.0 µg/m³Garden City, 9 September: 17.2 µg/m³Garden City, 10 September: 26.7 µg/m³, 5.3× its usual 4.8Garden City, 11 September: 13.7 µg/m³Garden City, 12 September: 5.8 µg/m³Garden City, 13 September: 3.5 µg/m³Garden City, 14 September: 5.1 µg/m³Twin FallsTwin Falls, 1 September: 15.5 µg/m³Twin Falls, 2 September: 11.2 µg/m³Twin Falls, 3 September: 34.7 µg/m³Twin Falls, 4 September: 49.3 µg/m³, 9.7× its usual 5.1Twin Falls, 5 September: 30.5 µg/m³, 6.0× its usual 5.1Twin Falls, 6 September: 17.0 µg/m³Twin Falls, 7 September: 18.0 µg/m³Twin Falls, 8 September: 16.5 µg/m³Twin Falls, 9 September: 14.7 µg/m³Twin Falls, 10 September: 20.5 µg/m³Twin Falls, 11 September: 30.6 µg/m³, 6.1× its usual 5.0Twin Falls, 12 September: 9.2 µg/m³Twin Falls, 13 September: 6.6 µg/m³Twin Falls, 14 September: 11.9 µg/m³NampaNampa, 1 September: 48.8 µg/m³Nampa, 2 September: 13.0 µg/m³Nampa, 3 September: 23.6 µg/m³Nampa, 4 September: 31.2 µg/m³, 4.4× its usual 7.1Nampa, 5 September: 48.2 µg/m³, 6.9× its usual 7.0Nampa, 6 September: 20.0 µg/m³Nampa, 7 September: 12.8 µg/m³Nampa, 8 September: 13.9 µg/m³Nampa, 9 September: 17.9 µg/m³Nampa, 10 September: 22.7 µg/m³Nampa, 11 September: 20.2 µg/m³Nampa, 12 September: 7.2 µg/m³Nampa, 13 September: 8.2 µg/m³Nampa, 14 September: 4.4 µg/m³Stansbury parkStansbury park, 1 September: 9.3 µg/m³Stansbury park, 2 September: 10.6 µg/m³Stansbury park, 3 September: 5.2 µg/m³Stansbury park, 4 September: 30.7 µg/m³, 5.6× its usual 5.5Stansbury park, 5 September: 23.7 µg/m³Stansbury park, 6 September: 13.3 µg/m³Stansbury park, 7 September: 11.5 µg/m³Stansbury park, 8 September: 14.0 µg/m³Stansbury park, 9 September: 8.1 µg/m³Stansbury park, 10 September: 8.4 µg/m³Stansbury park, 11 September: 41.9 µg/m³, 7.6× its usual 5.5Stansbury park, 12 September: 7.4 µg/m³Stansbury park, 13 September: 4.2 µg/m³Stansbury park, 14 September: 6.2 µg/m³TooeleTooele, 1 September: 9.3 µg/m³Tooele, 2 September: 10.6 µg/m³Tooele, 3 September: 5.2 µg/m³Tooele, 4 September: 30.7 µg/m³, 5.6× its usual 5.5Tooele, 5 September: 23.7 µg/m³Tooele, 6 September: 13.3 µg/m³Tooele, 7 September: 11.5 µg/m³Tooele, 8 September: 14.0 µg/m³Tooele, 9 September: 8.1 µg/m³Tooele, 10 September: 8.4 µg/m³Tooele, 11 September: 41.9 µg/m³, 7.6× its usual 5.5Tooele, 12 September: 7.4 µg/m³Tooele, 13 September: 4.2 µg/m³Tooele, 14 September: 6.2 µg/m³MillcreekMillcreek, 1 September: 11.8 µg/m³Millcreek, 2 September: 7.1 µg/m³Millcreek, 3 September: 7.3 µg/m³Millcreek, 4 September: 27.5 µg/m³, 3.8× its usual 7.3Millcreek, 5 September: 21.1 µg/m³Millcreek, 6 September: 12.1 µg/m³Millcreek, 7 September: 12.8 µg/m³Millcreek, 8 September: 12.4 µg/m³Millcreek, 9 September: 10.5 µg/m³Millcreek, 10 September: 9.5 µg/m³Millcreek, 11 September: 37.8 µg/m³, 5.0× its usual 7.5Millcreek, 12 September: 10.0 µg/m³Millcreek, 13 September: 7.3 µg/m³Millcreek, 14 September: 11.6 µg/m³PocatelloPocatello, 1 September: 10.4 µg/m³Pocatello, 2 September: 6.6 µg/m³Pocatello, 3 September: 11.4 µg/m³Pocatello, 4 September: 35.8 µg/m³, 7.0× its usual 5.1Pocatello, 5 September: 18.4 µg/m³Pocatello, 6 September: 9.4 µg/m³Pocatello, 7 September: 8.0 µg/m³Pocatello, 8 September: 8.6 µg/m³Pocatello, 9 September: 6.3 µg/m³Pocatello, 10 September: 7.6 µg/m³Pocatello, 11 September: 9.8 µg/m³Pocatello, 12 September: 7.5 µg/m³Pocatello, 13 September: 4.5 µg/m³Pocatello, 14 September: 4.4 µg/m³MagnaMagna, 1 September: 10.6 µg/m³Magna, 2 September: 5.9 µg/m³Magna, 3 September: 5.6 µg/m³Magna, 4 September: 27.5 µg/m³, 4.9× its usual 5.6Magna, 5 September: 17.3 µg/m³Magna, 6 September: 6.6 µg/m³Magna, 7 September: 8.9 µg/m³Magna, 8 September: 10.9 µg/m³Magna, 9 September: 8.7 µg/m³Magna, 10 September: 6.2 µg/m³Magna, 11 September: 34.3 µg/m³, 6.1× its usual 5.6Magna, 12 September: 7.8 µg/m³Magna, 13 September: 4.2 µg/m³Magna, 14 September: 7.2 µg/m³Salt Lake CitySalt Lake City, 1 September: 10.2 µg/m³Salt Lake City, 2 September: 6.4 µg/m³Salt Lake City, 3 September: 5.1 µg/m³Salt Lake City, 4 September: 28.3 µg/m³, 4.9× its usual 5.8Salt Lake City, 5 September: 19.2 µg/m³Salt Lake City, 6 September: 10.4 µg/m³Salt Lake City, 7 September: 11.2 µg/m³Salt Lake City, 8 September: 10.4 µg/m³Salt Lake City, 9 September: 8.4 µg/m³Salt Lake City, 10 September: 6.7 µg/m³Salt Lake City, 11 September: 33.3 µg/m³, 5.6× its usual 6.0Salt Lake City, 12 September: 8.7 µg/m³Salt Lake City, 13 September: 6.2 µg/m³Salt Lake City, 14 September: 8.6 µg/m³West Valley CityWest Valley City, 1 September: 11.3 µg/m³West Valley City, 2 September: 6.0 µg/m³West Valley City, 3 September: 4.1 µg/m³West Valley City, 4 September: 25.9 µg/m³, 4.2× its usual 6.1West Valley City, 5 September: 18.4 µg/m³West Valley City, 6 September: 9.1 µg/m³West Valley City, 7 September: 10.2 µg/m³West Valley City, 8 September: 10.8 µg/m³West Valley City, 9 September: 7.7 µg/m³West Valley City, 10 September: 5.6 µg/m³West Valley City, 11 September: 32.4 µg/m³, 5.2× its usual 6.2West Valley City, 12 September: 7.8 µg/m³West Valley City, 13 September: 5.4 µg/m³West Valley City, 14 September: 9.2 µg/m³SmithfieldSmithfield, 1 September: 10.0 µg/m³Smithfield, 2 September: 7.2 µg/m³Smithfield, 3 September: 7.8 µg/m³Smithfield, 4 September: 31.4 µg/m³, 5.2× its usual 6.0Smithfield, 5 September: 20.2 µg/m³Smithfield, 6 September: 9.1 µg/m³Smithfield, 7 September: 11.5 µg/m³Smithfield, 8 September: 10.7 µg/m³Smithfield, 9 September: 8.7 µg/m³Smithfield, 10 September: 8.0 µg/m³Smithfield, 11 September: 21.8 µg/m³Smithfield, 12 September: 6.4 µg/m³Smithfield, 13 September: 7.4 µg/m³Smithfield, 14 September: 2.7 µg/m³BurleyBurley, 1 September: 11.3 µg/m³Burley, 2 September: 8.2 µg/m³Burley, 3 September: 15.1 µg/m³Burley, 4 September: 29.3 µg/m³, 3.6× its usual 8.2Burley, 5 September: 18.2 µg/m³Burley, 6 September: 9.9 µg/m³Burley, 7 September: 10.6 µg/m³Burley, 8 September: 10.5 µg/m³Burley, 9 September: 8.7 µg/m³Burley, 10 September: 10.2 µg/m³Burley, 11 September: 11.8 µg/m³Burley, 12 September: 8.2 µg/m³Burley, 13 September: 7.5 µg/m³Burley, 14 September: 8.3 µg/m³BountifulBountiful, 1 September: 7.6 µg/m³Bountiful, 2 September: 5.4 µg/m³Bountiful, 3 September: 5.8 µg/m³Bountiful, 4 September: 26.1 µg/m³, 4.7× its usual 5.5Bountiful, 5 September: 9.4 µg/m³Bountiful, 6 September: 7.6 µg/m³Bountiful, 7 September: 10.2 µg/m³Bountiful, 8 September: 10.3 µg/m³Bountiful, 9 September: 7.3 µg/m³Bountiful, 10 September: 6.6 µg/m³Bountiful, 11 September: 29.2 µg/m³, 5.1× its usual 5.7Bountiful, 12 September: 11.2 µg/m³Bountiful, 13 September: 6.0 µg/m³Bountiful, 14 September: 8.5 µg/m³North OgdenNorth Ogden, 1 September: 8.4 µg/m³North Ogden, 2 September: 6.4 µg/m³North Ogden, 3 September: 3.9 µg/m³North Ogden, 4 September: 26.6 µg/m³, 5.3× its usual 4.6North Ogden, 5 September: 9.9 µg/m³North Ogden, 6 September: 8.4 µg/m³North Ogden, 7 September: 9.2 µg/m³North Ogden, 8 September: 9.5 µg/m³North Ogden, 9 September: 5.9 µg/m³North Ogden, 10 September: 6.6 µg/m³North Ogden, 11 September: 27.6 µg/m³, 5.5× its usual 4.8North Ogden, 12 September: 7.4 µg/m³North Ogden, 13 September: 4.1 µg/m³North Ogden, 14 September: 6.5 µg/m³PrinevillePrineville, 1 September: 11.4 µg/m³Prineville, 2 September: 9.2 µg/m³Prineville, 3 September: 8.3 µg/m³Prineville, 4 September: 49.6 µg/m³Prineville, 5 September: 87.0 µg/m³, 17× its usual 5.2Prineville, 6 September: 81.1 µg/m³, 16× its usual 5.2Prineville, 7 September: 52.4 µg/m³, 10× its usual 5.2Prineville, 8 September: 41.6 µg/m³, 8.0× its usual 5.2Prineville, 9 September: 25.2 µg/m³, 4.9× its usual 5.1Prineville, 10 September: 15.8 µg/m³Prineville, 11 September: 11.8 µg/m³Prineville, 12 September: 1.3 µg/m³Prineville, 13 September: 3.6 µg/m³Prineville, 14 September: 4.4 µg/m³BendBend, 1 September: 8.7 µg/m³Bend, 2 September: 9.4 µg/m³Bend, 3 September: 7.3 µg/m³Bend, 4 September: 18.1 µg/m³Bend, 5 September: 31.4 µg/m³, 5.0× its usual 6.3Bend, 6 September: 39.9 µg/m³, 6.8× its usual 5.9Bend, 7 September: 34.8 µg/m³, 6.1× its usual 5.7Bend, 8 September: 50.2 µg/m³, 9.0× its usual 5.6Bend, 9 September: 65.7 µg/m³, 12× its usual 5.5Bend, 10 September: 46.7 µg/m³, 8.5× its usual 5.5Bend, 11 September: 36.9 µg/m³Bend, 12 September: 9.2 µg/m³Bend, 13 September: 40.3 µg/m³Bend, 14 September: 16.5 µg/m³MadrasMadras, 1 September: 9.9 µg/m³Madras, 2 September: 8.9 µg/m³Madras, 3 September: 4.9 µg/m³Madras, 4 September: 14.8 µg/m³Madras, 5 September: 33.2 µg/m³, 5.0× its usual 6.6Madras, 6 September: 51.8 µg/m³, 7.8× its usual 6.6Madras, 7 September: 33.4 µg/m³, 5.2× its usual 6.4Madras, 8 September: 32.0 µg/m³, 5.0× its usual 6.4Madras, 9 September: 19.5 µg/m³Madras, 10 September: 7.9 µg/m³Madras, 11 September: 8.0 µg/m³Madras, 12 September: 2.1 µg/m³Madras, 13 September: 5.0 µg/m³Madras, 14 September: 4.0 µg/m³RedmondRedmond, 1 September: 10.1 µg/m³Redmond, 2 September: 11.0 µg/m³Redmond, 3 September: 7.0 µg/m³Redmond, 4 September: 31.5 µg/m³Redmond, 5 September: 39.2 µg/m³, 5.4× its usual 7.2Redmond, 6 September: 50.1 µg/m³, 7.3× its usual 6.9Redmond, 7 September: 42.0 µg/m³, 6.3× its usual 6.7Redmond, 8 September: 34.3 µg/m³, 5.3× its usual 6.5Redmond, 9 September: 38.7 µg/m³, 6.0× its usual 6.5Redmond, 10 September: 35.9 µg/m³, 5.5× its usual 6.5Redmond, 11 September: 14.5 µg/m³Redmond, 12 September: 4.4 µg/m³Redmond, 13 September: 10.4 µg/m³Redmond, 14 September: 10.8 µg/m³Cottage GroveCottage Grove, 1 September: 4.5 µg/m³Cottage Grove, 2 September: 1.8 µg/m³Cottage Grove, 3 September: 3.3 µg/m³Cottage Grove, 4 September: 11.4 µg/m³Cottage Grove, 5 September: 26.4 µg/m³, 5.2× its usual 5.1Cottage Grove, 6 September: 20.5 µg/m³Cottage Grove, 7 September: 17.5 µg/m³Cottage Grove, 8 September: 11.8 µg/m³Cottage Grove, 9 September: 8.0 µg/m³Cottage Grove, 10 September: 3.2 µg/m³Cottage Grove, 11 September: 2.3 µg/m³Cottage Grove, 12 September: 2.0 µg/m³Cottage Grove, 13 September: 5.3 µg/m³Cottage Grove, 14 September: 3.1 µg/m³MoscowMoscow, 1 September: 15.7 µg/m³Moscow, 2 September: 18.8 µg/m³Moscow, 3 September: 13.0 µg/m³Moscow, 4 September: 11.4 µg/m³Moscow, 5 September: 13.5 µg/m³Moscow, 6 September: 25.5 µg/m³, 3.5× its usual 7.3Moscow, 7 September: 31.6 µg/m³, 4.4× its usual 7.2Moscow, 8 September: 41.1 µg/m³, 5.6× its usual 7.3Moscow, 9 September: 22.5 µg/m³Moscow, 10 September: 8.2 µg/m³Moscow, 11 September: 16.6 µg/m³Moscow, 12 September: 5.5 µg/m³Moscow, 13 September: 6.5 µg/m³Moscow, 14 September: 6.2 µg/m³WeiserWeiser, 1 September: 60.5 µg/m³Weiser, 2 September: 21.4 µg/m³Weiser, 3 September: 17.4 µg/m³Weiser, 4 September: 13.2 µg/m³Weiser, 5 September: 23.5 µg/m³Weiser, 6 September: 25.9 µg/m³, 2.9× its usual 8.9Weiser, 7 September: 17.7 µg/m³Weiser, 8 September: 23.1 µg/m³Weiser, 9 September: 19.1 µg/m³Weiser, 10 September: 36.3 µg/m³, 4.1× its usual 8.8Weiser, 11 September: 20.6 µg/m³Weiser, 12 September: 8.7 µg/m³Weiser, 13 September: 10.3 µg/m³Weiser, 14 September: 10.3 µg/m³Baker CityBaker City, 1 September: 26.1 µg/m³Baker City, 2 September: 16.5 µg/m³Baker City, 3 September: 18.8 µg/m³Baker City, 4 September: 13.3 µg/m³Baker City, 5 September: 19.3 µg/m³Baker City, 6 September: 32.0 µg/m³, 4.7× its usual 6.8Baker City, 7 September: 32.5 µg/m³, 4.9× its usual 6.7Baker City, 8 September: 20.4 µg/m³Baker City, 9 September: 26.3 µg/m³, 4.1× its usual 6.4Baker City, 10 September: 27.0 µg/m³, 4.2× its usual 6.4Baker City, 11 September: 9.8 µg/m³Baker City, 12 September: 6.3 µg/m³Baker City, 13 September: 6.9 µg/m³Baker City, 14 September: 9.1 µg/m³TigardTigard, 1 September: 7.0 µg/m³Tigard, 2 September: 5.3 µg/m³Tigard, 3 September: 4.1 µg/m³Tigard, 4 September: 9.7 µg/m³Tigard, 5 September: 22.1 µg/m³Tigard, 6 September: 29.5 µg/m³, 5.1× its usual 5.8Tigard, 7 September: 23.0 µg/m³Tigard, 8 September: 12.5 µg/m³Tigard, 9 September: 4.6 µg/m³Tigard, 10 September: 4.7 µg/m³Tigard, 11 September: 4.2 µg/m³Tigard, 12 September: 4.6 µg/m³Tigard, 13 September: 6.1 µg/m³Tigard, 14 September: 4.6 µg/m³BeavertonBeaverton, 1 September: 5.5 µg/m³Beaverton, 2 September: 3.7 µg/m³Beaverton, 3 September: 2.4 µg/m³Beaverton, 4 September: 6.2 µg/m³Beaverton, 5 September: 16.1 µg/m³Beaverton, 6 September: 28.2 µg/m³, 5.6× its usual 4.3Beaverton, 7 September: 19.6 µg/m³Beaverton, 8 September: 9.8 µg/m³Beaverton, 9 September: 2.9 µg/m³Beaverton, 10 September: 2.9 µg/m³Beaverton, 11 September: 2.6 µg/m³Beaverton, 12 September: 3.0 µg/m³Beaverton, 13 September: 3.9 µg/m³Beaverton, 14 September: 2.8 µg/m³La GrandeLa Grande, 1 September: 14.8 µg/m³La Grande, 2 September: 14.2 µg/m³La Grande, 3 September: 17.1 µg/m³La Grande, 4 September: 14.2 µg/m³La Grande, 5 September: 17.7 µg/m³La Grande, 6 September: 27.8 µg/m³, 4.8× its usual 5.8La Grande, 7 September: 28.1 µg/m³, 4.9× its usual 5.7La Grande, 8 September: 20.8 µg/m³La Grande, 9 September: 15.1 µg/m³La Grande, 10 September: 15.3 µg/m³La Grande, 11 September: 11.2 µg/m³La Grande, 12 September: 3.0 µg/m³La Grande, 13 September: 4.7 µg/m³La Grande, 14 September: 7.1 µg/m³EugeneEugene, 1 September: 5.3 µg/m³Eugene, 2 September: 3.2 µg/m³Eugene, 3 September: 4.1 µg/m³Eugene, 4 September: 11.6 µg/m³Eugene, 5 September: 23.4 µg/m³Eugene, 6 September: 27.6 µg/m³, 5.0× its usual 5.5Eugene, 7 September: 18.2 µg/m³Eugene, 8 September: 10.4 µg/m³Eugene, 9 September: 5.7 µg/m³Eugene, 10 September: 4.9 µg/m³Eugene, 11 September: 4.0 µg/m³Eugene, 12 September: 3.1 µg/m³Eugene, 13 September: 6.5 µg/m³Eugene, 14 September: 4.5 µg/m³VancouverVancouver, 1 September: 5.5 µg/m³Vancouver, 2 September: 3.0 µg/m³Vancouver, 3 September: 1.1 µg/m³Vancouver, 4 September: 4.0 µg/m³Vancouver, 5 September: 14.3 µg/m³Vancouver, 6 September: 27.2 µg/m³, 4.9× its usual 5.6Vancouver, 7 September: 15.1 µg/m³Vancouver, 8 September: 6.7 µg/m³Vancouver, 9 September: 2.4 µg/m³Vancouver, 10 September: 2.6 µg/m³Vancouver, 11 September: 2.3 µg/m³Vancouver, 12 September: 2.3 µg/m³Vancouver, 13 September: 3.5 µg/m³Vancouver, 14 September: 1.7 µg/m³CanbyCanby, 1 September: 6.0 µg/m³Canby, 2 September: 4.1 µg/m³Canby, 3 September: 3.0 µg/m³Canby, 4 September: 7.9 µg/m³Canby, 5 September: 18.4 µg/m³Canby, 6 September: 26.7 µg/m³, 5.3× its usual 4.9Canby, 7 September: 21.1 µg/m³Canby, 8 September: 10.6 µg/m³Canby, 9 September: 4.2 µg/m³Canby, 10 September: 3.9 µg/m³Canby, 11 September: 3.2 µg/m³Canby, 12 September: no readingCanby, 13 September: no readingCanby, 14 September: no readingMilwaukieMilwaukie, 1 September: 5.6 µg/m³Milwaukie, 2 September: 4.2 µg/m³Milwaukie, 3 September: 3.3 µg/m³Milwaukie, 4 September: 6.0 µg/m³Milwaukie, 5 September: no readingMilwaukie, 6 September: 26.5 µg/m³, 5.3× its usual 4.1Milwaukie, 7 September: 17.6 µg/m³Milwaukie, 8 September: 8.8 µg/m³Milwaukie, 9 September: no readingMilwaukie, 10 September: no readingMilwaukie, 11 September: 3.4 µg/m³Milwaukie, 12 September: 3.8 µg/m³Milwaukie, 13 September: no readingMilwaukie, 14 September: 3.6 µg/m³PortlandPortland, 1 September: 5.9 µg/m³Portland, 2 September: 3.7 µg/m³Portland, 3 September: 2.6 µg/m³Portland, 4 September: 5.9 µg/m³Portland, 5 September: 15.5 µg/m³Portland, 6 September: 25.4 µg/m³, 5.1× its usual 4.7Portland, 7 September: 17.9 µg/m³Portland, 8 September: 8.4 µg/m³Portland, 9 September: 3.4 µg/m³Portland, 10 September: 3.7 µg/m³Portland, 11 September: 2.6 µg/m³Portland, 12 September: 2.8 µg/m³Portland, 13 September: 4.0 µg/m³Portland, 14 September: 2.8 µg/m³SilvertonSilverton, 1 September: 5.3 µg/m³Silverton, 2 September: 3.9 µg/m³Silverton, 3 September: 2.9 µg/m³Silverton, 4 September: 8.6 µg/m³Silverton, 5 September: 19.4 µg/m³Silverton, 6 September: 25.4 µg/m³, 5.1× its usual 4.4Silverton, 7 September: 16.5 µg/m³Silverton, 8 September: 8.5 µg/m³Silverton, 9 September: 4.4 µg/m³Silverton, 10 September: 3.6 µg/m³Silverton, 11 September: 2.7 µg/m³Silverton, 12 September: 3.2 µg/m³Silverton, 13 September: 4.7 µg/m³Silverton, 14 September: 3.5 µg/m³ButteButte, 1 September: 19.7 µg/m³Butte, 2 September: 31.7 µg/m³Butte, 3 September: 12.3 µg/m³Butte, 4 September: 10.3 µg/m³Butte, 5 September: 10.1 µg/m³Butte, 6 September: 16.4 µg/m³Butte, 7 September: 28.0 µg/m³, 5.5× its usual 5.1Butte, 8 September: 27.6 µg/m³, 5.5× its usual 5.0Butte, 9 September: 70.5 µg/m³, 14× its usual 4.9Butte, 10 September: 79.7 µg/m³Butte, 11 September: 34.7 µg/m³Butte, 12 September: 5.0 µg/m³Butte, 13 September: 3.5 µg/m³Butte, 14 September: 6.3 µg/m³HelenaHelena, 1 September: 13.7 µg/m³Helena, 2 September: 35.7 µg/m³Helena, 3 September: 20.6 µg/m³Helena, 4 September: 13.4 µg/m³Helena, 5 September: 12.4 µg/m³Helena, 6 September: 18.4 µg/m³Helena, 7 September: 28.3 µg/m³, 4.0× its usual 7.0Helena, 8 September: 39.3 µg/m³, 5.6× its usual 7.0Helena, 9 September: 69.2 µg/m³, 9.9× its usual 7.0Helena, 10 September: 25.1 µg/m³Helena, 11 September: 27.7 µg/m³Helena, 12 September: 8.6 µg/m³Helena, 13 September: 8.1 µg/m³Helena, 14 September: 9.8 µg/m³Helena Valley West …Helena Valley West Central, 1 September: 13.7 µg/m³Helena Valley West Central, 2 September: 35.7 µg/m³Helena Valley West Central, 3 September: 20.6 µg/m³Helena Valley West Central, 4 September: 13.4 µg/m³Helena Valley West Central, 5 September: 12.4 µg/m³Helena Valley West Central, 6 September: 18.4 µg/m³Helena Valley West Central, 7 September: 28.3 µg/m³, 4.0× its usual 7.0Helena Valley West Central, 8 September: 39.3 µg/m³, 5.6× its usual 7.0Helena Valley West Central, 9 September: 69.2 µg/m³, 9.9× its usual 7.0Helena Valley West Central, 10 September: 25.1 µg/m³Helena Valley West Central, 11 September: 27.7 µg/m³Helena Valley West Central, 12 September: 8.6 µg/m³Helena Valley West Central, 13 September: 8.1 µg/m³Helena Valley West Central, 14 September: 9.8 µg/m³MissoulaMissoula, 1 September: 20.0 µg/m³Missoula, 2 September: 35.4 µg/m³Missoula, 3 September: 19.9 µg/m³Missoula, 4 September: 13.5 µg/m³Missoula, 5 September: 11.7 µg/m³Missoula, 6 September: 16.7 µg/m³Missoula, 7 September: 26.3 µg/m³, 5.1× its usual 5.2Missoula, 8 September: 51.6 µg/m³, 10× its usual 5.1Missoula, 9 September: 57.5 µg/m³, 12× its usual 5.0Missoula, 10 September: 29.4 µg/m³Missoula, 11 September: 28.1 µg/m³Missoula, 12 September: 2.1 µg/m³Missoula, 13 September: 2.3 µg/m³Missoula, 14 September: 5.4 µg/m³LewistonLewiston, 1 September: 15.0 µg/m³Lewiston, 2 September: 21.7 µg/m³Lewiston, 3 September: 8.3 µg/m³Lewiston, 4 September: 12.6 µg/m³Lewiston, 5 September: 14.8 µg/m³Lewiston, 6 September: 22.7 µg/m³Lewiston, 7 September: 37.8 µg/m³, 4.3× its usual 8.7Lewiston, 8 September: 44.3 µg/m³, 5.1× its usual 8.7Lewiston, 9 September: 37.6 µg/m³, 4.4× its usual 8.5Lewiston, 10 September: 10.6 µg/m³Lewiston, 11 September: 21.5 µg/m³Lewiston, 12 September: 4.6 µg/m³Lewiston, 13 September: 4.9 µg/m³Lewiston, 14 September: 6.2 µg/m³PullmanPullman, 1 September: 11.1 µg/m³Pullman, 2 September: 16.8 µg/m³Pullman, 3 September: 10.0 µg/m³Pullman, 4 September: 10.3 µg/m³Pullman, 5 September: 11.1 µg/m³Pullman, 6 September: 24.8 µg/m³Pullman, 7 September: 33.3 µg/m³, 5.5× its usual 6.1Pullman, 8 September: 33.6 µg/m³, 5.5× its usual 6.1Pullman, 9 September: 16.7 µg/m³Pullman, 10 September: 4.5 µg/m³Pullman, 11 September: 15.2 µg/m³Pullman, 12 September: 3.0 µg/m³Pullman, 13 September: 3.9 µg/m³Pullman, 14 September: 4.2 µg/m³SpokaneSpokane, 1 September: 6.6 µg/m³Spokane, 2 September: 11.6 µg/m³Spokane, 3 September: 12.1 µg/m³Spokane, 4 September: 11.6 µg/m³Spokane, 5 September: 9.3 µg/m³Spokane, 6 September: 12.9 µg/m³Spokane, 7 September: 26.0 µg/m³, 3.9× its usual 6.7Spokane, 8 September: 22.8 µg/m³Spokane, 9 September: 17.7 µg/m³Spokane, 10 September: 5.3 µg/m³Spokane, 11 September: 5.2 µg/m³Spokane, 12 September: 3.7 µg/m³Spokane, 13 September: 4.1 µg/m³Spokane, 14 September: 4.5 µg/m³The DallesThe Dalles, 1 September: 6.9 µg/m³The Dalles, 2 September: 7.3 µg/m³The Dalles, 3 September: 3.3 µg/m³The Dalles, 4 September: 6.4 µg/m³The Dalles, 5 September: 13.3 µg/m³The Dalles, 6 September: 19.3 µg/m³The Dalles, 7 September: 20.3 µg/m³The Dalles, 8 September: 31.9 µg/m³, 6.4× its usual 4.8The Dalles, 9 September: 8.2 µg/m³The Dalles, 10 September: 5.4 µg/m³The Dalles, 11 September: 5.0 µg/m³The Dalles, 12 September: 3.5 µg/m³The Dalles, 13 September: 4.5 µg/m³The Dalles, 14 September: 4.3 µg/m³HermistonHermiston, 1 September: 7.7 µg/m³Hermiston, 2 September: 9.8 µg/m³Hermiston, 3 September: 7.6 µg/m³Hermiston, 4 September: 15.1 µg/m³Hermiston, 5 September: 11.3 µg/m³Hermiston, 6 September: 15.4 µg/m³Hermiston, 7 September: 23.7 µg/m³Hermiston, 8 September: 31.1 µg/m³, 5.2× its usual 6.0Hermiston, 9 September: 12.9 µg/m³Hermiston, 10 September: 6.5 µg/m³Hermiston, 11 September: 5.1 µg/m³Hermiston, 12 September: 2.9 µg/m³Hermiston, 13 September: 4.1 µg/m³Hermiston, 14 September: 4.0 µg/m³PendletonPendleton, 1 September: 6.9 µg/m³Pendleton, 2 September: 9.2 µg/m³Pendleton, 3 September: 13.3 µg/m³Pendleton, 4 September: 15.7 µg/m³Pendleton, 5 September: 11.9 µg/m³Pendleton, 6 September: 16.3 µg/m³Pendleton, 7 September: 23.8 µg/m³Pendleton, 8 September: 30.9 µg/m³, 6.2× its usual 4.9Pendleton, 9 September: 19.2 µg/m³Pendleton, 10 September: 5.3 µg/m³Pendleton, 11 September: 4.7 µg/m³Pendleton, 12 September: 2.6 µg/m³Pendleton, 13 September: 3.7 µg/m³Pendleton, 14 September: 3.9 µg/m³ToppenishToppenish, 1 September: 10.8 µg/m³Toppenish, 2 September: 11.2 µg/m³Toppenish, 3 September: 6.8 µg/m³Toppenish, 4 September: 8.7 µg/m³Toppenish, 5 September: 12.4 µg/m³Toppenish, 6 September: 18.5 µg/m³Toppenish, 7 September: 24.4 µg/m³Toppenish, 8 September: 30.5 µg/m³, 3.9× its usual 7.8Toppenish, 9 September: 16.8 µg/m³Toppenish, 10 September: 5.3 µg/m³Toppenish, 11 September: 2.8 µg/m³Toppenish, 12 September: 2.9 µg/m³Toppenish, 13 September: 5.7 µg/m³Toppenish, 14 September: 5.8 µg/m³YakimaYakima, 1 September: 6.6 µg/m³Yakima, 2 September: 7.4 µg/m³Yakima, 3 September: 3.5 µg/m³Yakima, 4 September: 4.6 µg/m³Yakima, 5 September: 7.2 µg/m³Yakima, 6 September: 13.8 µg/m³Yakima, 7 September: 18.6 µg/m³Yakima, 8 September: 27.8 µg/m³, 4.3× its usual 6.4Yakima, 9 September: 10.2 µg/m³Yakima, 10 September: 2.0 µg/m³Yakima, 11 September: 2.6 µg/m³Yakima, 12 September: 3.0 µg/m³Yakima, 13 September: 4.1 µg/m³Yakima, 14 September: 2.5 µg/m³ProsserProsser, 1 September: 7.4 µg/m³Prosser, 2 September: 11.6 µg/m³Prosser, 3 September: 6.6 µg/m³Prosser, 4 September: 8.5 µg/m³Prosser, 5 September: 12.2 µg/m³Prosser, 6 September: 12.8 µg/m³Prosser, 7 September: 19.1 µg/m³Prosser, 8 September: 26.9 µg/m³, 3.8× its usual 7.0Prosser, 9 September: 14.1 µg/m³Prosser, 10 September: 3.8 µg/m³Prosser, 11 September: 4.3 µg/m³Prosser, 12 September: 2.5 µg/m³Prosser, 13 September: 3.3 µg/m³Prosser, 14 September: 4.7 µg/m³MedfordMedford, 1 September: 7.4 µg/m³Medford, 2 September: 4.5 µg/m³Medford, 3 September: 5.1 µg/m³Medford, 4 September: 15.5 µg/m³Medford, 5 September: 19.8 µg/m³Medford, 6 September: 15.7 µg/m³Medford, 7 September: 15.9 µg/m³Medford, 8 September: 26.4 µg/m³, 4.9× its usual 5.4Medford, 9 September: 18.1 µg/m³Medford, 10 September: 9.1 µg/m³Medford, 11 September: 2.8 µg/m³Medford, 12 September: 2.9 µg/m³Medford, 13 September: 5.3 µg/m³Medford, 14 September: 5.2 µg/m³AshlandAshland, 1 September: 6.2 µg/m³Ashland, 2 September: 4.5 µg/m³Ashland, 3 September: 4.6 µg/m³Ashland, 4 September: 12.8 µg/m³Ashland, 5 September: 17.7 µg/m³Ashland, 6 September: 11.8 µg/m³Ashland, 7 September: 16.8 µg/m³Ashland, 8 September: 26.2 µg/m³, 5.1× its usual 5.1Ashland, 9 September: 14.4 µg/m³Ashland, 10 September: 9.2 µg/m³Ashland, 11 September: 2.6 µg/m³Ashland, 12 September: 2.9 µg/m³Ashland, 13 September: 4.7 µg/m³Ashland, 14 September: 4.3 µg/m³TalentTalent, 1 September: 6.3 µg/m³Talent, 2 September: 4.0 µg/m³Talent, 3 September: 4.1 µg/m³Talent, 4 September: 13.2 µg/m³Talent, 5 September: 17.5 µg/m³Talent, 6 September: 13.0 µg/m³Talent, 7 September: 15.5 µg/m³Talent, 8 September: 25.6 µg/m³, 5.1× its usual 4.6Talent, 9 September: 13.5 µg/m³Talent, 10 September: 8.9 µg/m³Talent, 11 September: 2.2 µg/m³Talent, 12 September: 2.4 µg/m³Talent, 13 September: 4.2 µg/m³Talent, 14 September: 4.0 µg/m³SunnysideSunnyside, 1 September: 7.9 µg/m³Sunnyside, 2 September: 12.4 µg/m³Sunnyside, 3 September: 6.9 µg/m³Sunnyside, 4 September: 9.5 µg/m³Sunnyside, 5 September: 10.4 µg/m³Sunnyside, 6 September: 15.5 µg/m³Sunnyside, 7 September: 21.6 µg/m³Sunnyside, 8 September: 25.6 µg/m³, 3.3× its usual 7.8Sunnyside, 9 September: 16.2 µg/m³Sunnyside, 10 September: 4.7 µg/m³Sunnyside, 11 September: 3.5 µg/m³Sunnyside, 12 September: 4.0 µg/m³Sunnyside, 13 September: 3.8 µg/m³Sunnyside, 14 September: 4.4 µg/m³LewistownLewistown, 1 September: 5.5 µg/m³Lewistown, 2 September: 12.1 µg/m³Lewistown, 3 September: 13.8 µg/m³Lewistown, 4 September: 7.0 µg/m³Lewistown, 5 September: 6.4 µg/m³Lewistown, 6 September: 7.8 µg/m³Lewistown, 7 September: 8.6 µg/m³Lewistown, 8 September: 22.3 µg/m³Lewistown, 9 September: 60.2 µg/m³, 10× its usual 5.8Lewistown, 10 September: 19.3 µg/m³Lewistown, 11 September: 16.6 µg/m³Lewistown, 12 September: 9.9 µg/m³Lewistown, 13 September: 2.4 µg/m³Lewistown, 14 September: 3.8 µg/m³Miles CityMiles City, 1 September: 4.6 µg/m³Miles City, 2 September: 9.6 µg/m³Miles City, 3 September: 11.4 µg/m³Miles City, 4 September: no readingMiles City, 5 September: no readingMiles City, 6 September: 5.6 µg/m³Miles City, 7 September: 7.7 µg/m³Miles City, 8 September: 9.7 µg/m³Miles City, 9 September: 53.7 µg/m³, 7.1× its usual 7.6Miles City, 10 September: 60.8 µg/m³Miles City, 11 September: 31.5 µg/m³Miles City, 12 September: 15.9 µg/m³Miles City, 13 September: 3.8 µg/m³Miles City, 14 September: 3.8 µg/m³HavreHavre, 1 September: 3.3 µg/m³Havre, 2 September: 4.5 µg/m³Havre, 3 September: 5.9 µg/m³Havre, 4 September: 5.1 µg/m³Havre, 5 September: 4.0 µg/m³Havre, 6 September: 4.4 µg/m³Havre, 7 September: 4.8 µg/m³Havre, 8 September: 5.3 µg/m³Havre, 9 September: 39.9 µg/m³, 8.0× its usual 4.6Havre, 10 September: 4.4 µg/m³Havre, 11 September: 11.7 µg/m³Havre, 12 September: 5.4 µg/m³Havre, 13 September: 3.5 µg/m³Havre, 14 September: 2.8 µg/m³BozemanBozeman, 1 September: 8.6 µg/m³Bozeman, 2 September: 10.4 µg/m³Bozeman, 3 September: 7.8 µg/m³Bozeman, 4 September: 9.0 µg/m³Bozeman, 5 September: 9.3 µg/m³Bozeman, 6 September: 13.1 µg/m³Bozeman, 7 September: 18.8 µg/m³Bozeman, 8 September: 24.7 µg/m³Bozeman, 9 September: 38.2 µg/m³, 6.6× its usual 5.8Bozeman, 10 September: 56.5 µg/m³Bozeman, 11 September: 13.2 µg/m³Bozeman, 12 September: 9.8 µg/m³Bozeman, 13 September: 5.9 µg/m³Bozeman, 14 September: 5.8 µg/m³GlendiveGlendive, 1 September: 3.1 µg/m³Glendive, 2 September: 4.2 µg/m³Glendive, 3 September: 9.8 µg/m³Glendive, 4 September: 39.0 µg/m³Glendive, 5 September: 4.0 µg/m³Glendive, 6 September: 4.3 µg/m³Glendive, 7 September: 4.3 µg/m³Glendive, 8 September: 4.8 µg/m³Glendive, 9 September: 37.7 µg/m³, 7.4× its usual 5.1Glendive, 10 September: 37.9 µg/m³Glendive, 11 September: 27.1 µg/m³Glendive, 12 September: 17.1 µg/m³Glendive, 13 September: 2.9 µg/m³Glendive, 14 September: 3.1 µg/m³BillingsBillings, 1 September: 7.1 µg/m³Billings, 2 September: 14.2 µg/m³Billings, 3 September: 7.6 µg/m³Billings, 4 September: no readingBillings, 5 September: 8.2 µg/m³Billings, 6 September: 9.4 µg/m³Billings, 7 September: 13.1 µg/m³Billings, 8 September: 19.0 µg/m³Billings, 9 September: 32.6 µg/m³, 4.9× its usual 6.7Billings, 10 September: 36.9 µg/m³Billings, 11 September: 15.9 µg/m³Billings, 12 September: 3.9 µg/m³Billings, 13 September: 3.1 µg/m³Billings, 14 September: 6.4 µg/m³LockwoodLockwood, 1 September: 7.1 µg/m³Lockwood, 2 September: 14.2 µg/m³Lockwood, 3 September: 7.6 µg/m³Lockwood, 4 September: no readingLockwood, 5 September: 8.2 µg/m³Lockwood, 6 September: 9.4 µg/m³Lockwood, 7 September: 13.1 µg/m³Lockwood, 8 September: 19.0 µg/m³Lockwood, 9 September: 32.6 µg/m³, 4.9× its usual 6.7Lockwood, 10 September: 36.9 µg/m³Lockwood, 11 September: 15.9 µg/m³Lockwood, 12 September: 3.9 µg/m³Lockwood, 13 September: 3.1 µg/m³Lockwood, 14 September: 6.4 µg/m³HerrimanHerriman, 1 September: 6.5 µg/m³Herriman, 2 September: 5.1 µg/m³Herriman, 3 September: 4.4 µg/m³Herriman, 4 September: 22.5 µg/m³Herriman, 5 September: 18.1 µg/m³Herriman, 6 September: 8.0 µg/m³Herriman, 7 September: 7.9 µg/m³Herriman, 8 September: 9.0 µg/m³Herriman, 9 September: 7.6 µg/m³Herriman, 10 September: 5.1 µg/m³Herriman, 11 September: 37.2 µg/m³, 7.2× its usual 5.2Herriman, 12 September: 8.9 µg/m³Herriman, 13 September: 1.8 µg/m³Herriman, 14 September: 0.9 µg/m³West JordanWest Jordan, 1 September: 10.5 µg/m³West Jordan, 2 September: 6.4 µg/m³West Jordan, 3 September: 5.8 µg/m³West Jordan, 4 September: 24.4 µg/m³West Jordan, 5 September: 21.1 µg/m³West Jordan, 6 September: 9.0 µg/m³West Jordan, 7 September: 10.8 µg/m³West Jordan, 8 September: 10.0 µg/m³West Jordan, 9 September: 7.4 µg/m³West Jordan, 10 September: 6.6 µg/m³West Jordan, 11 September: 34.0 µg/m³, 5.2× its usual 6.5West Jordan, 12 September: 9.1 µg/m³West Jordan, 13 September: 7.0 µg/m³West Jordan, 14 September: 9.6 µg/m³OremOrem, 1 September: 9.1 µg/m³Orem, 2 September: 7.1 µg/m³Orem, 3 September: 6.2 µg/m³Orem, 4 September: 16.3 µg/m³Orem, 5 September: 24.1 µg/m³Orem, 6 September: 9.1 µg/m³Orem, 7 September: 10.7 µg/m³Orem, 8 September: 11.7 µg/m³Orem, 9 September: 8.4 µg/m³Orem, 10 September: 7.5 µg/m³Orem, 11 September: 31.1 µg/m³, 5.6× its usual 5.6Orem, 12 September: 11.4 µg/m³Orem, 13 September: 5.8 µg/m³Orem, 14 September: 8.9 µg/m³Spanish ForkSpanish Fork, 1 September: 7.1 µg/m³Spanish Fork, 2 September: 6.1 µg/m³Spanish Fork, 3 September: 6.5 µg/m³Spanish Fork, 4 September: 18.9 µg/m³Spanish Fork, 5 September: 21.2 µg/m³Spanish Fork, 6 September: 8.1 µg/m³Spanish Fork, 7 September: 9.5 µg/m³Spanish Fork, 8 September: 10.3 µg/m³Spanish Fork, 9 September: 9.1 µg/m³Spanish Fork, 10 September: 6.8 µg/m³Spanish Fork, 11 September: 29.9 µg/m³, 5.2× its usual 5.8Spanish Fork, 12 September: 14.0 µg/m³Spanish Fork, 13 September: 5.2 µg/m³Spanish Fork, 14 September: 7.4 µg/m³1 Sep35791113
The 60 cities with the highest readings of 63, 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
PrinevilleOregon, United States5 87.05 September5.217×
ButteMontana, United States3 70.59 September4.914×
MeridianIdaho, United States4 84.85 September6.214×
BendOregon, United States6 65.79 September5.512×
MissoulaMontana, United States3 57.59 September5.012×
Garden CityIdaho, United States4 53.55 September5.111×
LewistownMontana, United States1 60.29 September5.810×
HelenaMontana, United States3 69.29 September7.09.9×
Helena Valley West CentralMontana, United States3 69.29 September7.09.9×
Twin FallsIdaho, United States3 49.34 September5.19.7×
HavreMontana, United States1 39.99 September4.68.0×
MadrasOregon, United States4 51.86 September6.67.8×
Stansbury parkUtah, United States2 41.911 September5.57.6×
TooeleUtah, United States2 41.911 September5.57.6×
GlendiveMontana, United States1 37.79 September5.17.4×
RedmondOregon, United States6 50.16 September6.97.3×
HerrimanUtah, United States1 37.211 September5.27.2×
Miles CityMontana, United States1 53.79 September7.67.1×
PocatelloIdaho, United States1 35.84 September5.17.0×
NampaIdaho, United States2 48.25 September7.06.9×
BozemanMontana, United States1 38.29 September5.86.6×
The DallesOregon, United States1 31.98 September4.86.4×
PendletonOregon, United States1 30.98 September4.96.2×
MagnaUtah, United States2 34.311 September5.66.1×
MoscowIdaho, United States3 41.18 September7.35.6×
Salt Lake CityUtah, United States2 33.311 September6.05.6×
OremUtah, United States1 31.111 September5.65.6×
BeavertonOregon, United States1 28.26 September4.35.6×
PullmanWashington, United States2 33.68 September6.15.5×
North OgdenUtah, United States2 27.611 September4.85.5×
CanbyOregon, United States1 26.76 September4.95.3×
MilwaukieOregon, United States1 26.56 September4.15.3×
West JordanUtah, United States1 34.011 September6.55.2×
West Valley CityUtah, United States2 32.411 September6.25.2×
SmithfieldUtah, United States1 31.44 September6.05.2×
HermistonOregon, United States1 31.18 September6.05.2×
Spanish ForkUtah, United States1 29.911 September5.85.2×
Cottage GroveOregon, United States1 26.45 September5.15.2×
LewistonIdaho, United States3 44.38 September8.75.1×
TigardOregon, United States1 29.56 September5.85.1×
BountifulUtah, United States2 29.211 September5.75.1×
AshlandOregon, United States1 26.28 September5.15.1×
TalentOregon, United States1 25.68 September4.65.1×
PortlandOregon, United States1 25.46 September4.75.1×
SilvertonOregon, United States1 25.46 September4.45.1×
MillcreekUtah, United States2 37.811 September7.55.0×
EugeneOregon, United States1 27.66 September5.55.0×
PrestonIdaho, United States1 25.04 September3.45.0×
BillingsMontana, United States1 32.69 September6.74.9×
LockwoodMontana, United States1 32.69 September6.74.9×
Baker CityOregon, United States4 32.57 September6.74.9×
La GrandeOregon, United States2 28.17 September5.74.9×
VancouverWashington, United States1 27.26 September5.64.9×
MedfordOregon, United States1 26.48 September5.44.9×
YakimaWashington, United States1 27.88 September6.44.3×
WeiserIdaho, United States2 36.310 September8.84.1×
ToppenishWashington, United States1 30.58 September7.83.9×
SpokaneWashington, United States1 26.07 September6.73.9×
ProsserWashington, United States1 26.98 September7.03.8×
BurleyIdaho, United States1 29.34 September8.23.6×
Medicine HatAlberta, Canada1 25.19 September6.93.6×
Columbia FallsMontana, United States1 25.09 September6.93.6×
SunnysideWashington, United States1 25.68 September7.83.3×

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 25 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.

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SmogRank, North-western United States and Canada, 4 to 11 September 2024: 63 cities with PM2.5 at twice their usual or more, 4 to 11 September 2024, smogrank.com/episodes/2024-09-04-north-western-united-states-and-canada (accessed 5 October 2026).

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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.