SmogRank / Episodes / Canada

North-western Canada and United States, September 2025

For 8 days, from 6 to 13 September 2025, 57 cities in Canada and the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Ephrata, Washington, United States: 103.0 µg/m³ on 6 September, about 16× its usual 6.3. Ended 13 September.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached57in 2 countries
Days86 to 13 September 2025
Worst day6 September40 cities counted
Furthest above usual16×Ephrata

Day by day

6 September 40 cities at twice their usual or more
AirdrieMedicine HatHavreMoses LakeBozemanLewistownFort McMurrayLa GrandeSwift CurrentPendletonChilliwackAbbotsfordBillingsMissionLockwoodNorth BendLyndenMarysvilleMount VernonBellinghamLangleyKirklandInglewood-Finn HillPicnic Point-North LynnwoodBellevuePort CoquitlamCoquitlamAnacortesRentonShorelineSeattleAuburnOak HarborStrawberry HillWhite CenterBurienThe DallesBurnabyNorth VancouverPort TownsendDeltaVancouverTacomaHood RiverRichmondParklandBremertonVictoriaLaceyLangfordPort AngelesSheltonNorth CowichanDuncanCentraliaChehalisNanaimoHarewoodGreshamSalmon CreekLongviewRidgefieldVancouverNorth PortlandMiles CityPortlandMilwaukieOregon CityReginaBeavertonTigardCanbyHillsboroAberdeenWoodburnForest GroveSilvertonPort AlberniMcMinnvilleGlendiveCampbell RiverEstevanKitimatTerraceFlin FlonGreat FallsSaskatoonRed DeerCalgaryPrince AlbertHelena Valley West CentralHelenaKamloopsFort SaskatchewanMoscowLewistonEdmontonGrand CentreAgassizSherwood ParkDrayton ValleyWalla WallaSt. AlbertVernonHermistonGibsonsKelownaSunnysidePullmanCoeur d'AleneColumbia FallsLethbridgeWest VancouverPrince GeorgeToppenishButteFort St. JohnYakimaProsserMissoulaSpokane ValleyAirway HeightsSpokaneSandpointHopeSmithersEdsonCastlegarSquamishCrestonMeadEllensburgTri-CitiesQuesnelCranbrookQuincyGrande PrairieWhistlerWilliams LakeWenatcheeEphrata
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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

EphrataEphrata, 3 September: 20.5 µg/m³Ephrata, 4 September: 27.7 µg/m³Ephrata, 5 September: 53.9 µg/m³Ephrata, 6 September: 103.0 µg/m³, 16× its usual 6.3Ephrata, 7 September: 56.4 µg/m³, 9.0× its usual 6.3Ephrata, 8 September: 26.4 µg/m³, 4.2× its usual 6.3Ephrata, 9 September: 11.4 µg/m³Ephrata, 10 September: 15.5 µg/m³Ephrata, 11 September: 16.3 µg/m³Ephrata, 12 September: 15.9 µg/m³Ephrata, 13 September: 13.9 µg/m³Ephrata, 14 September: 15.5 µg/m³Ephrata, 15 September: 13.1 µg/m³Ephrata, 16 September: 7.2 µg/m³WenatcheeWenatchee, 3 September: 20.3 µg/m³Wenatchee, 4 September: 36.2 µg/m³Wenatchee, 5 September: 58.2 µg/m³Wenatchee, 6 September: 83.3 µg/m³, 16× its usual 5.2Wenatchee, 7 September: 20.4 µg/m³Wenatchee, 8 September: 22.1 µg/m³Wenatchee, 9 September: 21.6 µg/m³Wenatchee, 10 September: 17.0 µg/m³Wenatchee, 11 September: 18.1 µg/m³Wenatchee, 12 September: 13.9 µg/m³Wenatchee, 13 September: 19.2 µg/m³Wenatchee, 14 September: 11.8 µg/m³Wenatchee, 15 September: 5.0 µg/m³Wenatchee, 16 September: 9.0 µg/m³WhistlerWhistler, 3 September: 34.7 µg/m³Whistler, 4 September: 38.4 µg/m³Whistler, 5 September: 56.3 µg/m³Whistler, 6 September: 65.5 µg/m³, 13× its usual 4.3Whistler, 7 September: 12.5 µg/m³Whistler, 8 September: 4.6 µg/m³Whistler, 9 September: 5.8 µg/m³Whistler, 10 September: 8.7 µg/m³Whistler, 11 September: 7.0 µg/m³Whistler, 12 September: 7.9 µg/m³Whistler, 13 September: 6.3 µg/m³Whistler, 14 September: 3.4 µg/m³Whistler, 15 September: 0.7 µg/m³Whistler, 16 September: 2.3 µg/m³QuincyQuincy, 3 September: 16.4 µg/m³Quincy, 4 September: 24.6 µg/m³Quincy, 5 September: 37.5 µg/m³Quincy, 6 September: 58.8 µg/m³, 11× its usual 5.6Quincy, 7 September: 19.0 µg/m³Quincy, 8 September: 17.5 µg/m³Quincy, 9 September: 14.9 µg/m³Quincy, 10 September: 20.5 µg/m³Quincy, 11 September: 16.5 µg/m³Quincy, 12 September: 10.4 µg/m³Quincy, 13 September: 9.1 µg/m³Quincy, 14 September: 9.2 µg/m³Quincy, 15 September: 4.5 µg/m³Quincy, 16 September: 5.3 µg/m³CastlegarCastlegar, 3 September: 16.7 µg/m³Castlegar, 4 September: 22.6 µg/m³Castlegar, 5 September: 44.2 µg/m³Castlegar, 6 September: 54.2 µg/m³, 7.1× its usual 7.6Castlegar, 7 September: 56.1 µg/m³, 7.4× its usual 7.6Castlegar, 8 September: 31.6 µg/m³, 4.2× its usual 7.6Castlegar, 9 September: 24.3 µg/m³Castlegar, 10 September: 15.0 µg/m³Castlegar, 11 September: 14.8 µg/m³Castlegar, 12 September: 32.4 µg/m³Castlegar, 13 September: 45.1 µg/m³Castlegar, 14 September: 33.9 µg/m³Castlegar, 15 September: 15.1 µg/m³Castlegar, 16 September: 11.5 µg/m³SandpointSandpoint, 3 September: 27.6 µg/m³Sandpoint, 4 September: 33.0 µg/m³Sandpoint, 5 September: 38.8 µg/m³Sandpoint, 6 September: 50.5 µg/m³, 6.6× its usual 7.6Sandpoint, 7 September: 26.1 µg/m³, 3.5× its usual 7.5Sandpoint, 8 September: 19.0 µg/m³Sandpoint, 9 September: 20.9 µg/m³Sandpoint, 10 September: 17.8 µg/m³Sandpoint, 11 September: 17.9 µg/m³Sandpoint, 12 September: 20.0 µg/m³Sandpoint, 13 September: 21.4 µg/m³Sandpoint, 14 September: 15.7 µg/m³Sandpoint, 15 September: 9.5 µg/m³Sandpoint, 16 September: 9.9 µg/m³SquamishSquamish, 3 September: 173.0 µg/m³Squamish, 4 September: 53.1 µg/m³Squamish, 5 September: 43.1 µg/m³Squamish, 6 September: 49.3 µg/m³, 7.5× its usual 6.6Squamish, 7 September: 11.8 µg/m³Squamish, 8 September: 8.2 µg/m³Squamish, 9 September: 9.4 µg/m³Squamish, 10 September: 7.7 µg/m³Squamish, 11 September: 8.6 µg/m³Squamish, 12 September: 7.6 µg/m³Squamish, 13 September: 8.8 µg/m³Squamish, 14 September: 4.7 µg/m³Squamish, 15 September: 5.8 µg/m³Squamish, 16 September: 7.6 µg/m³ToppenishToppenish, 3 September: 25.1 µg/m³Toppenish, 4 September: 45.5 µg/m³Toppenish, 5 September: 48.2 µg/m³Toppenish, 6 September: 44.8 µg/m³, 6.0× its usual 7.5Toppenish, 7 September: 22.5 µg/m³Toppenish, 8 September: 12.1 µg/m³Toppenish, 9 September: 8.0 µg/m³Toppenish, 10 September: 15.9 µg/m³Toppenish, 11 September: 19.4 µg/m³Toppenish, 12 September: 19.7 µg/m³Toppenish, 13 September: 17.6 µg/m³Toppenish, 14 September: 6.3 µg/m³Toppenish, 15 September: 7.6 µg/m³Toppenish, 16 September: 11.5 µg/m³CrestonCreston, 3 September: 14.1 µg/m³Creston, 4 September: 26.7 µg/m³Creston, 5 September: 26.7 µg/m³Creston, 6 September: 44.0 µg/m³, 7.6× its usual 5.8Creston, 7 September: 43.4 µg/m³, 7.6× its usual 5.7Creston, 8 September: 28.3 µg/m³, 5.0× its usual 5.7Creston, 9 September: 19.1 µg/m³Creston, 10 September: 10.5 µg/m³Creston, 11 September: 22.0 µg/m³Creston, 12 September: 13.7 µg/m³Creston, 13 September: 18.9 µg/m³Creston, 14 September: 14.3 µg/m³Creston, 15 September: 5.8 µg/m³Creston, 16 September: 6.6 µg/m³SpokaneSpokane, 3 September: 30.0 µg/m³Spokane, 4 September: 31.6 µg/m³Spokane, 5 September: 37.7 µg/m³Spokane, 6 September: 43.5 µg/m³, 6.6× its usual 6.6Spokane, 7 September: 16.0 µg/m³Spokane, 8 September: 8.2 µg/m³Spokane, 9 September: 14.2 µg/m³Spokane, 10 September: 23.0 µg/m³Spokane, 11 September: 11.3 µg/m³Spokane, 12 September: 12.0 µg/m³Spokane, 13 September: 14.6 µg/m³Spokane, 14 September: 8.2 µg/m³Spokane, 15 September: 5.0 µg/m³Spokane, 16 September: 7.9 µg/m³HopeHope, 3 September: 28.0 µg/m³Hope, 4 September: 25.7 µg/m³Hope, 5 September: 69.1 µg/m³Hope, 6 September: 43.1 µg/m³, 7.2× its usual 6.0Hope, 7 September: 9.5 µg/m³Hope, 8 September: 6.8 µg/m³Hope, 9 September: 9.7 µg/m³Hope, 10 September: 34.4 µg/m³Hope, 11 September: 8.0 µg/m³Hope, 12 September: 6.5 µg/m³Hope, 13 September: 5.2 µg/m³Hope, 14 September: 3.8 µg/m³Hope, 15 September: 3.0 µg/m³Hope, 16 September: 6.6 µg/m³Airway HeightsAirway Heights, 3 September: no readingAirway Heights, 4 September: 25.0 µg/m³Airway Heights, 5 September: 35.9 µg/m³Airway Heights, 6 September: 42.3 µg/m³, 6.6× its usual 6.4Airway Heights, 7 September: 15.1 µg/m³Airway Heights, 8 September: 7.8 µg/m³Airway Heights, 9 September: 14.8 µg/m³Airway Heights, 10 September: 20.3 µg/m³Airway Heights, 11 September: 12.3 µg/m³Airway Heights, 12 September: 11.5 µg/m³Airway Heights, 13 September: 13.0 µg/m³Airway Heights, 14 September: 7.8 µg/m³Airway Heights, 15 September: 5.9 µg/m³Airway Heights, 16 September: 6.4 µg/m³EllensburgEllensburg, 3 September: 14.8 µg/m³Ellensburg, 4 September: 23.7 µg/m³Ellensburg, 5 September: 40.1 µg/m³Ellensburg, 6 September: 41.3 µg/m³, 7.9× its usual 5.2Ellensburg, 7 September: 7.3 µg/m³Ellensburg, 8 September: 7.7 µg/m³Ellensburg, 9 September: 6.2 µg/m³Ellensburg, 10 September: 11.2 µg/m³Ellensburg, 11 September: 13.0 µg/m³Ellensburg, 12 September: 7.3 µg/m³Ellensburg, 13 September: 7.3 µg/m³Ellensburg, 14 September: 5.5 µg/m³Ellensburg, 15 September: 2.7 µg/m³Ellensburg, 16 September: 4.5 µg/m³MeadMead, 3 September: 26.0 µg/m³Mead, 4 September: 35.5 µg/m³Mead, 5 September: 37.3 µg/m³Mead, 6 September: 41.0 µg/m³, 7.9× its usual 5.2Mead, 7 September: 19.1 µg/m³Mead, 8 September: 9.4 µg/m³Mead, 9 September: 15.1 µg/m³Mead, 10 September: 22.1 µg/m³Mead, 11 September: 13.8 µg/m³Mead, 12 September: 13.4 µg/m³Mead, 13 September: 15.0 µg/m³Mead, 14 September: 8.9 µg/m³Mead, 15 September: 5.8 µg/m³Mead, 16 September: 5.8 µg/m³ProsserProsser, 3 September: 23.2 µg/m³Prosser, 4 September: 26.0 µg/m³Prosser, 5 September: 34.2 µg/m³Prosser, 6 September: 40.6 µg/m³, 6.2× its usual 6.5Prosser, 7 September: 12.9 µg/m³Prosser, 8 September: 8.8 µg/m³Prosser, 9 September: 5.0 µg/m³Prosser, 10 September: 10.7 µg/m³Prosser, 11 September: 10.7 µg/m³Prosser, 12 September: 9.8 µg/m³Prosser, 13 September: 11.3 µg/m³Prosser, 14 September: 4.9 µg/m³Prosser, 15 September: 4.8 µg/m³Prosser, 16 September: 9.3 µg/m³Tri-CitiesTri-Cities, 3 September: 19.8 µg/m³Tri-Cities, 4 September: 19.8 µg/m³Tri-Cities, 5 September: 34.8 µg/m³Tri-Cities, 6 September: 40.2 µg/m³, 8.0× its usual 4.7Tri-Cities, 7 September: 15.1 µg/m³Tri-Cities, 8 September: 8.4 µg/m³Tri-Cities, 9 September: 6.0 µg/m³Tri-Cities, 10 September: 10.2 µg/m³Tri-Cities, 11 September: 11.5 µg/m³Tri-Cities, 12 September: 9.9 µg/m³Tri-Cities, 13 September: 10.8 µg/m³Tri-Cities, 14 September: 4.2 µg/m³Tri-Cities, 15 September: 4.7 µg/m³Tri-Cities, 16 September: 6.8 µg/m³SunnysideSunnyside, 3 September: 25.9 µg/m³Sunnyside, 4 September: no readingSunnyside, 5 September: no readingSunnyside, 6 September: 39.8 µg/m³, 5.2× its usual 7.6Sunnyside, 7 September: 18.2 µg/m³Sunnyside, 8 September: 12.5 µg/m³Sunnyside, 9 September: 7.3 µg/m³Sunnyside, 10 September: 14.3 µg/m³Sunnyside, 11 September: 16.0 µg/m³Sunnyside, 12 September: 15.0 µg/m³Sunnyside, 13 September: 11.6 µg/m³Sunnyside, 14 September: 5.5 µg/m³Sunnyside, 15 September: 7.5 µg/m³Sunnyside, 16 September: 9.3 µg/m³CranbrookCranbrook, 3 September: 16.3 µg/m³Cranbrook, 4 September: 25.4 µg/m³Cranbrook, 5 September: 25.5 µg/m³Cranbrook, 6 September: 39.3 µg/m³, 6.0× its usual 6.6Cranbrook, 7 September: 56.2 µg/m³, 8.8× its usual 6.4Cranbrook, 8 September: 30.0 µg/m³, 4.7× its usual 6.4Cranbrook, 9 September: 18.6 µg/m³Cranbrook, 10 September: 12.2 µg/m³Cranbrook, 11 September: 12.5 µg/m³Cranbrook, 12 September: 14.8 µg/m³Cranbrook, 13 September: 14.8 µg/m³Cranbrook, 14 September: 19.2 µg/m³Cranbrook, 15 September: 5.5 µg/m³Cranbrook, 16 September: 10.2 µg/m³Spokane ValleySpokane Valley, 3 September: 26.6 µg/m³Spokane Valley, 4 September: 29.5 µg/m³Spokane Valley, 5 September: 37.2 µg/m³Spokane Valley, 6 September: 39.0 µg/m³, 6.5× its usual 6.0Spokane Valley, 7 September: 18.0 µg/m³Spokane Valley, 8 September: 7.6 µg/m³Spokane Valley, 9 September: 12.0 µg/m³Spokane Valley, 10 September: 20.8 µg/m³Spokane Valley, 11 September: 11.5 µg/m³Spokane Valley, 12 September: 12.0 µg/m³Spokane Valley, 13 September: 14.0 µg/m³Spokane Valley, 14 September: 6.8 µg/m³Spokane Valley, 15 September: 5.1 µg/m³Spokane Valley, 16 September: 7.3 µg/m³VernonVernon, 3 September: 18.8 µg/m³Vernon, 4 September: 27.5 µg/m³Vernon, 5 September: 42.4 µg/m³Vernon, 6 September: 38.4 µg/m³, 4.8× its usual 8.0Vernon, 7 September: 33.1 µg/m³, 4.2× its usual 7.8Vernon, 8 September: 11.8 µg/m³Vernon, 9 September: 11.2 µg/m³Vernon, 10 September: 12.0 µg/m³Vernon, 11 September: 17.8 µg/m³Vernon, 12 September: 16.3 µg/m³Vernon, 13 September: 16.8 µg/m³Vernon, 14 September: 11.8 µg/m³Vernon, 15 September: 8.3 µg/m³Vernon, 16 September: 9.3 µg/m³YakimaYakima, 3 September: 20.7 µg/m³Yakima, 4 September: 58.0 µg/m³Yakima, 5 September: 44.7 µg/m³Yakima, 6 September: 37.7 µg/m³, 6.2× its usual 6.1Yakima, 7 September: 21.3 µg/m³Yakima, 8 September: 10.3 µg/m³Yakima, 9 September: 9.5 µg/m³Yakima, 10 September: 10.9 µg/m³Yakima, 11 September: 18.6 µg/m³Yakima, 12 September: 15.0 µg/m³Yakima, 13 September: 15.3 µg/m³Yakima, 14 September: 7.5 µg/m³Yakima, 15 September: 7.5 µg/m³Yakima, 16 September: 7.9 µg/m³SmithersSmithers, 3 September: 25.3 µg/m³Smithers, 4 September: 26.1 µg/m³Smithers, 5 September: 36.6 µg/m³Smithers, 6 September: 37.1 µg/m³, 7.4× its usual 4.4Smithers, 7 September: 10.1 µg/m³Smithers, 8 September: 7.1 µg/m³Smithers, 9 September: 5.9 µg/m³Smithers, 10 September: 5.7 µg/m³Smithers, 11 September: 5.0 µg/m³Smithers, 12 September: 3.4 µg/m³Smithers, 13 September: 3.2 µg/m³Smithers, 14 September: 3.4 µg/m³Smithers, 15 September: 5.1 µg/m³Smithers, 16 September: 6.2 µg/m³Coeur d'AleneCoeur d'Alene, 3 September: 24.8 µg/m³Coeur d'Alene, 4 September: 29.8 µg/m³Coeur d'Alene, 5 September: 37.7 µg/m³Coeur d'Alene, 6 September: 36.8 µg/m³, 5.3× its usual 6.9Coeur d'Alene, 7 September: 15.7 µg/m³Coeur d'Alene, 8 September: 10.8 µg/m³Coeur d'Alene, 9 September: 18.9 µg/m³Coeur d'Alene, 10 September: 19.3 µg/m³Coeur d'Alene, 11 September: 15.2 µg/m³Coeur d'Alene, 12 September: 14.5 µg/m³Coeur d'Alene, 13 September: 15.7 µg/m³Coeur d'Alene, 14 September: 9.0 µg/m³Coeur d'Alene, 15 September: 7.0 µg/m³Coeur d'Alene, 16 September: 8.8 µg/m³KelownaKelowna, 3 September: 17.1 µg/m³Kelowna, 4 September: 23.2 µg/m³Kelowna, 5 September: 42.7 µg/m³Kelowna, 6 September: 35.0 µg/m³, 4.6× its usual 7.6Kelowna, 7 September: 37.7 µg/m³, 5.2× its usual 7.3Kelowna, 8 September: 13.6 µg/m³Kelowna, 9 September: 13.3 µg/m³Kelowna, 10 September: 14.8 µg/m³Kelowna, 11 September: 16.1 µg/m³Kelowna, 12 September: 13.5 µg/m³Kelowna, 13 September: 14.9 µg/m³Kelowna, 14 September: 10.8 µg/m³Kelowna, 15 September: 5.9 µg/m³Kelowna, 16 September: 9.2 µg/m³LewistonLewiston, 3 September: 14.8 µg/m³Lewiston, 4 September: 17.7 µg/m³Lewiston, 5 September: 35.1 µg/m³Lewiston, 6 September: 34.8 µg/m³, 4.1× its usual 8.5Lewiston, 7 September: 11.8 µg/m³Lewiston, 8 September: 9.6 µg/m³Lewiston, 9 September: 13.1 µg/m³Lewiston, 10 September: 18.4 µg/m³Lewiston, 11 September: 9.2 µg/m³Lewiston, 12 September: 9.2 µg/m³Lewiston, 13 September: 12.3 µg/m³Lewiston, 14 September: 8.4 µg/m³Lewiston, 15 September: 5.0 µg/m³Lewiston, 16 September: 6.2 µg/m³Columbia FallsColumbia Falls, 3 September: 27.8 µg/m³Columbia Falls, 4 September: 26.4 µg/m³Columbia Falls, 5 September: 27.9 µg/m³Columbia Falls, 6 September: 33.6 µg/m³, 4.9× its usual 6.9Columbia Falls, 7 September: 38.0 µg/m³, 5.5× its usual 6.9Columbia Falls, 8 September: 11.1 µg/m³Columbia Falls, 9 September: 11.0 µg/m³Columbia Falls, 10 September: 13.1 µg/m³Columbia Falls, 11 September: 11.8 µg/m³Columbia Falls, 12 September: 7.1 µg/m³Columbia Falls, 13 September: 8.6 µg/m³Columbia Falls, 14 September: 13.2 µg/m³Columbia Falls, 15 September: 7.2 µg/m³Columbia Falls, 16 September: 7.6 µg/m³MissoulaMissoula, 3 September: 16.2 µg/m³Missoula, 4 September: 27.6 µg/m³Missoula, 5 September: 24.8 µg/m³Missoula, 6 September: 33.4 µg/m³, 6.3× its usual 5.3Missoula, 7 September: 29.6 µg/m³, 5.6× its usual 5.3Missoula, 8 September: 5.9 µg/m³Missoula, 9 September: 9.9 µg/m³Missoula, 10 September: 8.2 µg/m³Missoula, 11 September: 2.9 µg/m³Missoula, 12 September: 3.9 µg/m³Missoula, 13 September: 4.6 µg/m³Missoula, 14 September: 7.3 µg/m³Missoula, 15 September: 2.6 µg/m³Missoula, 16 September: 4.9 µg/m³KamloopsKamloops, 3 September: 18.6 µg/m³Kamloops, 4 September: 33.3 µg/m³Kamloops, 5 September: 29.2 µg/m³Kamloops, 6 September: 33.4 µg/m³, 3.8× its usual 8.9Kamloops, 7 September: 33.9 µg/m³, 3.9× its usual 8.8Kamloops, 8 September: 13.6 µg/m³Kamloops, 9 September: 12.2 µg/m³Kamloops, 10 September: 8.5 µg/m³Kamloops, 11 September: 18.3 µg/m³Kamloops, 12 September: 19.6 µg/m³Kamloops, 13 September: 9.5 µg/m³Kamloops, 14 September: 6.1 µg/m³Kamloops, 15 September: 6.4 µg/m³Kamloops, 16 September: 9.0 µg/m³ButteButte, 3 September: 21.0 µg/m³Butte, 4 September: 24.3 µg/m³Butte, 5 September: 22.2 µg/m³Butte, 6 September: 31.9 µg/m³, 6.1× its usual 5.2Butte, 7 September: 30.2 µg/m³, 5.8× its usual 5.2Butte, 8 September: 6.8 µg/m³Butte, 9 September: 10.5 µg/m³Butte, 10 September: 6.3 µg/m³Butte, 11 September: 5.4 µg/m³Butte, 12 September: 3.2 µg/m³Butte, 13 September: 4.1 µg/m³Butte, 14 September: 4.0 µg/m³Butte, 15 September: 3.3 µg/m³Butte, 16 September: 4.5 µg/m³Prince GeorgePrince George, 3 September: 41.9 µg/m³Prince George, 4 September: 33.5 µg/m³Prince George, 5 September: 64.2 µg/m³Prince George, 6 September: 31.4 µg/m³, 3.5× its usual 9.0Prince George, 7 September: 49.8 µg/m³, 5.7× its usual 8.7Prince George, 8 September: 49.7 µg/m³, 5.8× its usual 8.5Prince George, 9 September: 29.0 µg/m³, 3.4× its usual 8.5Prince George, 10 September: 18.3 µg/m³Prince George, 11 September: 45.7 µg/m³, 5.4× its usual 8.4Prince George, 12 September: 44.6 µg/m³, 5.5× its usual 8.1Prince George, 13 September: 36.5 µg/m³, 5.0× its usual 7.3Prince George, 14 September: 13.8 µg/m³Prince George, 15 September: 5.9 µg/m³Prince George, 16 September: 16.6 µg/m³PullmanPullman, 3 September: 14.7 µg/m³Pullman, 4 September: 15.8 µg/m³Pullman, 5 September: 34.2 µg/m³Pullman, 6 September: 31.4 µg/m³, 5.3× its usual 5.9Pullman, 7 September: 11.2 µg/m³Pullman, 8 September: 9.4 µg/m³Pullman, 9 September: 10.4 µg/m³Pullman, 10 September: 14.3 µg/m³Pullman, 11 September: 8.3 µg/m³Pullman, 12 September: 8.7 µg/m³Pullman, 13 September: 13.6 µg/m³Pullman, 14 September: 6.4 µg/m³Pullman, 15 September: 4.7 µg/m³Pullman, 16 September: 5.2 µg/m³GibsonsGibsons, 3 September: 48.7 µg/m³Gibsons, 4 September: 37.9 µg/m³Gibsons, 5 September: 40.4 µg/m³Gibsons, 6 September: 31.2 µg/m³, 5.1× its usual 6.1Gibsons, 7 September: 10.5 µg/m³Gibsons, 8 September: 7.8 µg/m³Gibsons, 9 September: 8.5 µg/m³Gibsons, 10 September: 7.3 µg/m³Gibsons, 11 September: 8.4 µg/m³Gibsons, 12 September: 7.0 µg/m³Gibsons, 13 September: 7.5 µg/m³Gibsons, 14 September: 6.1 µg/m³Gibsons, 15 September: 5.1 µg/m³Gibsons, 16 September: 6.5 µg/m³CalgaryCalgary, 3 September: 57.2 µg/m³Calgary, 4 September: 47.8 µg/m³Calgary, 5 September: 37.0 µg/m³Calgary, 6 September: 31.2 µg/m³, 3.2× its usual 9.8Calgary, 7 September: 33.7 µg/m³, 3.4× its usual 9.8Calgary, 8 September: 32.1 µg/m³, 3.3× its usual 9.6Calgary, 9 September: 30.8 µg/m³, 3.2× its usual 9.5Calgary, 10 September: 25.2 µg/m³, 2.7× its usual 9.3Calgary, 11 September: 16.9 µg/m³Calgary, 12 September: 22.5 µg/m³Calgary, 13 September: 15.2 µg/m³Calgary, 14 September: 18.7 µg/m³Calgary, 15 September: 20.6 µg/m³Calgary, 16 September: 20.9 µg/m³HermistonHermiston, 3 September: 18.0 µg/m³Hermiston, 4 September: 18.5 µg/m³Hermiston, 5 September: 31.4 µg/m³Hermiston, 6 September: 29.3 µg/m³, 5.1× its usual 5.8Hermiston, 7 September: 14.7 µg/m³Hermiston, 8 September: 8.0 µg/m³Hermiston, 9 September: 6.1 µg/m³Hermiston, 10 September: 9.7 µg/m³Hermiston, 11 September: 15.2 µg/m³Hermiston, 12 September: 12.3 µg/m³Hermiston, 13 September: 14.1 µg/m³Hermiston, 14 September: 4.3 µg/m³Hermiston, 15 September: 3.9 µg/m³Hermiston, 16 September: 7.6 µg/m³MoscowMoscow, 3 September: 18.1 µg/m³Moscow, 4 September: 18.8 µg/m³Moscow, 5 September: 34.5 µg/m³Moscow, 6 September: 29.1 µg/m³, 4.0× its usual 7.2Moscow, 7 September: 12.2 µg/m³Moscow, 8 September: 11.0 µg/m³Moscow, 9 September: 15.3 µg/m³Moscow, 10 September: 16.5 µg/m³Moscow, 11 September: 10.5 µg/m³Moscow, 12 September: 8.5 µg/m³Moscow, 13 September: 14.6 µg/m³Moscow, 14 September: 8.3 µg/m³Moscow, 15 September: 7.2 µg/m³Moscow, 16 September: 6.6 µg/m³Grande PrairieGrande Prairie, 3 September: 47.0 µg/m³Grande Prairie, 4 September: 36.2 µg/m³Grande Prairie, 5 September: 23.5 µg/m³Grande Prairie, 6 September: 28.9 µg/m³, 3.9× its usual 7.4Grande Prairie, 7 September: 36.8 µg/m³, 5.3× its usual 7.0Grande Prairie, 8 September: 36.2 µg/m³, 5.3× its usual 6.8Grande Prairie, 9 September: 35.9 µg/m³, 5.3× its usual 6.8Grande Prairie, 10 September: 11.2 µg/m³Grande Prairie, 11 September: 20.5 µg/m³Grande Prairie, 12 September: 67.9 µg/m³, 11× its usual 6.3Grande Prairie, 13 September: 57.0 µg/m³, 9.2× its usual 6.2Grande Prairie, 14 September: 28.6 µg/m³Grande Prairie, 15 September: 5.3 µg/m³Grande Prairie, 16 September: 6.8 µg/m³West VancouverWest Vancouver, 3 September: 87.2 µg/m³West Vancouver, 4 September: 21.8 µg/m³West Vancouver, 5 September: 31.4 µg/m³West Vancouver, 6 September: 28.1 µg/m³, 5.6× its usual 4.9West Vancouver, 7 September: 9.6 µg/m³West Vancouver, 8 September: 6.7 µg/m³West Vancouver, 9 September: 7.3 µg/m³West Vancouver, 10 September: 5.0 µg/m³West Vancouver, 11 September: 6.7 µg/m³West Vancouver, 12 September: 6.0 µg/m³West Vancouver, 13 September: 6.1 µg/m³West Vancouver, 14 September: 5.0 µg/m³West Vancouver, 15 September: 4.2 µg/m³West Vancouver, 16 September: 5.1 µg/m³AgassizAgassiz, 3 September: 30.7 µg/m³Agassiz, 4 September: 37.0 µg/m³Agassiz, 5 September: 35.7 µg/m³Agassiz, 6 September: 27.5 µg/m³, 4.4× its usual 6.3Agassiz, 7 September: 8.9 µg/m³Agassiz, 8 September: 8.4 µg/m³Agassiz, 9 September: 11.2 µg/m³Agassiz, 10 September: 13.6 µg/m³Agassiz, 11 September: no readingAgassiz, 12 September: 6.5 µg/m³Agassiz, 13 September: 6.4 µg/m³Agassiz, 14 September: 4.9 µg/m³Agassiz, 15 September: 3.5 µg/m³Agassiz, 16 September: 7.1 µg/m³Walla WallaWalla Walla, 3 September: 14.0 µg/m³Walla Walla, 4 September: 15.7 µg/m³Walla Walla, 5 September: 27.1 µg/m³Walla Walla, 6 September: 26.3 µg/m³, 4.6× its usual 5.7Walla Walla, 7 September: 11.6 µg/m³Walla Walla, 8 September: 6.6 µg/m³Walla Walla, 9 September: 7.0 µg/m³Walla Walla, 10 September: 10.1 µg/m³Walla Walla, 11 September: 10.3 µg/m³Walla Walla, 12 September: 10.4 µg/m³Walla Walla, 13 September: 12.0 µg/m³Walla Walla, 14 September: 5.9 µg/m³Walla Walla, 15 September: 4.1 µg/m³Walla Walla, 16 September: 7.5 µg/m³QuesnelQuesnel, 3 September: 35.7 µg/m³Quesnel, 4 September: 30.5 µg/m³Quesnel, 5 September: 28.7 µg/m³Quesnel, 6 September: 25.1 µg/m³, 3.0× its usual 8.4Quesnel, 7 September: 55.3 µg/m³, 6.6× its usual 8.4Quesnel, 8 September: 68.2 µg/m³, 8.2× its usual 8.3Quesnel, 9 September: 36.4 µg/m³, 4.4× its usual 8.2Quesnel, 10 September: 43.6 µg/m³Quesnel, 11 September: 46.4 µg/m³, 5.7× its usual 8.2Quesnel, 12 September: 30.2 µg/m³, 3.7× its usual 8.2Quesnel, 13 September: 33.6 µg/m³, 4.3× its usual 7.9Quesnel, 14 September: 12.8 µg/m³Quesnel, 15 September: 5.0 µg/m³Quesnel, 16 September: 8.4 µg/m³Williams LakeWilliams Lake, 3 September: 34.3 µg/m³Williams Lake, 4 September: 35.7 µg/m³Williams Lake, 5 September: 26.3 µg/m³Williams Lake, 6 September: 22.3 µg/m³Williams Lake, 7 September: 48.3 µg/m³, 9.7× its usual 4.0Williams Lake, 8 September: 77.0 µg/m³, 15× its usual 3.8Williams Lake, 9 September: 52.2 µg/m³, 10× its usual 3.6Williams Lake, 10 September: 72.9 µg/m³Williams Lake, 11 September: 42.3 µg/m³, 8.5× its usual 3.5Williams Lake, 12 September: 42.1 µg/m³, 8.4× its usual 3.4Williams Lake, 13 September: 19.8 µg/m³Williams Lake, 14 September: 3.8 µg/m³Williams Lake, 15 September: 5.4 µg/m³Williams Lake, 16 September: 4.4 µg/m³LethbridgeLethbridge, 3 September: 62.0 µg/m³Lethbridge, 4 September: 40.9 µg/m³Lethbridge, 5 September: 30.6 µg/m³Lethbridge, 6 September: 19.8 µg/m³Lethbridge, 7 September: 39.5 µg/m³, 5.5× its usual 7.2Lethbridge, 8 September: 31.1 µg/m³, 4.4× its usual 7.0Lethbridge, 9 September: 18.3 µg/m³Lethbridge, 10 September: 14.8 µg/m³Lethbridge, 11 September: 15.5 µg/m³Lethbridge, 12 September: 10.9 µg/m³Lethbridge, 13 September: 9.3 µg/m³Lethbridge, 14 September: 19.9 µg/m³Lethbridge, 15 September: 12.8 µg/m³Lethbridge, 16 September: 16.7 µg/m³Fort St. JohnFort St. John, 3 September: 39.8 µg/m³Fort St. John, 4 September: 15.2 µg/m³Fort St. John, 5 September: 12.4 µg/m³Fort St. John, 6 September: 20.8 µg/m³Fort St. John, 7 September: 37.5 µg/m³, 6.1× its usual 6.1Fort St. John, 8 September: 26.8 µg/m³, 4.4× its usual 6.1Fort St. John, 9 September: 13.1 µg/m³Fort St. John, 10 September: 5.7 µg/m³Fort St. John, 11 September: 30.1 µg/m³, 4.9× its usual 6.1Fort St. John, 12 September: 7.7 µg/m³Fort St. John, 13 September: 2.7 µg/m³Fort St. John, 14 September: 9.2 µg/m³Fort St. John, 15 September: 3.5 µg/m³Fort St. John, 16 September: 4.8 µg/m³EdmontonEdmonton, 3 September: 48.2 µg/m³Edmonton, 4 September: 36.8 µg/m³Edmonton, 5 September: 14.3 µg/m³Edmonton, 6 September: 22.4 µg/m³Edmonton, 7 September: 36.8 µg/m³, 3.3× its usual 11.0Edmonton, 8 September: 39.1 µg/m³, 3.6× its usual 11.0Edmonton, 9 September: 45.1 µg/m³, 4.1× its usual 11.0Edmonton, 10 September: 35.3 µg/m³, 3.2× its usual 11.0Edmonton, 11 September: 28.5 µg/m³, 2.7× its usual 10.7Edmonton, 12 September: 25.3 µg/m³, 2.4× its usual 10.7Edmonton, 13 September: 22.0 µg/m³Edmonton, 14 September: 14.5 µg/m³Edmonton, 15 September: 14.0 µg/m³Edmonton, 16 September: 12.0 µg/m³Fort SaskatchewanFort Saskatchewan, 3 September: 44.3 µg/m³Fort Saskatchewan, 4 September: 34.8 µg/m³Fort Saskatchewan, 5 September: 13.2 µg/m³Fort Saskatchewan, 6 September: 20.0 µg/m³Fort Saskatchewan, 7 September: 31.7 µg/m³, 3.4× its usual 9.2Fort Saskatchewan, 8 September: 29.6 µg/m³, 3.2× its usual 9.2Fort Saskatchewan, 9 September: 36.1 µg/m³, 3.9× its usual 9.2Fort Saskatchewan, 10 September: 31.1 µg/m³, 3.4× its usual 9.2Fort Saskatchewan, 11 September: 21.0 µg/m³Fort Saskatchewan, 12 September: no readingFort Saskatchewan, 13 September: no readingFort Saskatchewan, 14 September: 13.0 µg/m³Fort Saskatchewan, 15 September: 11.0 µg/m³Fort Saskatchewan, 16 September: 9.6 µg/m³Great FallsGreat Falls, 3 September: 33.0 µg/m³Great Falls, 4 September: 29.7 µg/m³Great Falls, 5 September: no readingGreat Falls, 6 September: no readingGreat Falls, 7 September: 30.6 µg/m³, 2.7× its usual 11.3Great Falls, 8 September: 16.3 µg/m³Great Falls, 9 September: 14.5 µg/m³Great Falls, 10 September: 11.7 µg/m³Great Falls, 11 September: 13.2 µg/m³Great Falls, 12 September: 9.6 µg/m³Great Falls, 13 September: 9.1 µg/m³Great Falls, 14 September: 12.2 µg/m³Great Falls, 15 September: 7.1 µg/m³Great Falls, 16 September: 14.0 µg/m³HelenaHelena, 3 September: 25.3 µg/m³Helena, 4 September: 27.9 µg/m³Helena, 5 September: 23.2 µg/m³Helena, 6 September: 21.2 µg/m³Helena, 7 September: 29.8 µg/m³, 3.9× its usual 7.7Helena, 8 September: 6.7 µg/m³Helena, 9 September: 10.2 µg/m³Helena, 10 September: 6.5 µg/m³Helena, 11 September: 7.5 µg/m³Helena, 12 September: 4.3 µg/m³Helena, 13 September: 3.6 µg/m³Helena, 14 September: 3.9 µg/m³Helena, 15 September: 3.4 µg/m³Helena, 16 September: 6.5 µg/m³Helena Valley West …Helena Valley West Central, 3 September: 25.3 µg/m³Helena Valley West Central, 4 September: 27.9 µg/m³Helena Valley West Central, 5 September: 23.2 µg/m³Helena Valley West Central, 6 September: 21.2 µg/m³Helena Valley West Central, 7 September: 29.8 µg/m³, 3.9× its usual 7.7Helena Valley West Central, 8 September: 6.7 µg/m³Helena Valley West Central, 9 September: 10.2 µg/m³Helena Valley West Central, 10 September: 6.5 µg/m³Helena Valley West Central, 11 September: 7.5 µg/m³Helena Valley West Central, 12 September: 4.3 µg/m³Helena Valley West Central, 13 September: 3.6 µg/m³Helena Valley West Central, 14 September: 3.9 µg/m³Helena Valley West Central, 15 September: 3.4 µg/m³Helena Valley West Central, 16 September: 6.5 µg/m³St. AlbertSt. Albert, 3 September: 44.2 µg/m³St. Albert, 4 September: 33.6 µg/m³St. Albert, 5 September: 15.4 µg/m³St. Albert, 6 September: 21.3 µg/m³St. Albert, 7 September: 27.7 µg/m³, 3.6× its usual 7.7St. Albert, 8 September: 27.6 µg/m³, 3.6× its usual 7.7St. Albert, 9 September: 36.4 µg/m³, 4.8× its usual 7.6St. Albert, 10 September: 24.9 µg/m³St. Albert, 11 September: 20.7 µg/m³St. Albert, 12 September: 26.5 µg/m³, 3.7× its usual 7.2St. Albert, 13 September: 19.3 µg/m³St. Albert, 14 September: 12.5 µg/m³St. Albert, 15 September: 10.3 µg/m³St. Albert, 16 September: 8.9 µg/m³Sherwood ParkSherwood Park, 3 September: 42.7 µg/m³Sherwood Park, 4 September: 32.7 µg/m³Sherwood Park, 5 September: 10.3 µg/m³Sherwood Park, 6 September: 16.4 µg/m³Sherwood Park, 7 September: 26.1 µg/m³, 3.3× its usual 7.8Sherwood Park, 8 September: 27.2 µg/m³, 3.5× its usual 7.8Sherwood Park, 9 September: 34.6 µg/m³, 4.4× its usual 7.8Sherwood Park, 10 September: 28.8 µg/m³, 3.7× its usual 7.7Sherwood Park, 11 September: 21.4 µg/m³Sherwood Park, 12 September: 18.7 µg/m³Sherwood Park, 13 September: 16.5 µg/m³Sherwood Park, 14 September: 10.0 µg/m³Sherwood Park, 15 September: 9.3 µg/m³Sherwood Park, 16 September: 7.0 µg/m³EdsonEdson, 3 September: 37.2 µg/m³Edson, 4 September: 35.9 µg/m³Edson, 5 September: 18.2 µg/m³Edson, 6 September: 19.4 µg/m³Edson, 7 September: 18.6 µg/m³Edson, 8 September: 29.0 µg/m³, 4.5× its usual 6.4Edson, 9 September: 31.3 µg/m³, 4.9× its usual 6.4Edson, 10 September: 21.3 µg/m³Edson, 11 September: 23.2 µg/m³Edson, 12 September: 45.4 µg/m³, 7.4× its usual 6.1Edson, 13 September: 39.2 µg/m³, 6.9× its usual 5.7Edson, 14 September: 12.6 µg/m³Edson, 15 September: 7.8 µg/m³Edson, 16 September: 10.6 µg/m³Red DeerRed Deer, 3 September: 46.8 µg/m³Red Deer, 4 September: 35.7 µg/m³Red Deer, 5 September: 23.7 µg/m³Red Deer, 6 September: 21.7 µg/m³Red Deer, 7 September: 24.4 µg/m³Red Deer, 8 September: 28.4 µg/m³, 3.2× its usual 9.0Red Deer, 9 September: 30.5 µg/m³, 3.4× its usual 9.0Red Deer, 10 September: 26.5 µg/m³, 2.9× its usual 9.0Red Deer, 11 September: 22.2 µg/m³Red Deer, 12 September: 21.1 µg/m³Red Deer, 13 September: 13.0 µg/m³Red Deer, 14 September: 13.7 µg/m³Red Deer, 15 September: 18.7 µg/m³Red Deer, 16 September: 16.3 µg/m³Drayton ValleyDrayton Valley, 3 September: 33.9 µg/m³Drayton Valley, 4 September: 24.9 µg/m³Drayton Valley, 5 September: 17.1 µg/m³Drayton Valley, 6 September: 22.7 µg/m³Drayton Valley, 7 September: 22.4 µg/m³Drayton Valley, 8 September: 20.6 µg/m³Drayton Valley, 9 September: 34.8 µg/m³, 4.5× its usual 7.8Drayton Valley, 10 September: 13.2 µg/m³Drayton Valley, 11 September: 18.2 µg/m³Drayton Valley, 12 September: 19.4 µg/m³Drayton Valley, 13 September: 16.8 µg/m³Drayton Valley, 14 September: 11.6 µg/m³Drayton Valley, 15 September: 10.6 µg/m³Drayton Valley, 16 September: 11.9 µg/m³Grand CentreGrand Centre, 3 September: 33.1 µg/m³Grand Centre, 4 September: 17.6 µg/m³Grand Centre, 5 September: 8.0 µg/m³Grand Centre, 6 September: 5.8 µg/m³Grand Centre, 7 September: 12.3 µg/m³Grand Centre, 8 September: 22.6 µg/m³Grand Centre, 9 September: 24.9 µg/m³Grand Centre, 10 September: 26.1 µg/m³, 3.3× its usual 7.9Grand Centre, 11 September: 31.9 µg/m³, 4.2× its usual 7.6Grand Centre, 12 September: 19.5 µg/m³Grand Centre, 13 September: 19.9 µg/m³Grand Centre, 14 September: 6.2 µg/m³Grand Centre, 15 September: 10.2 µg/m³Grand Centre, 16 September: 14.8 µg/m³Prince AlbertPrince Albert, 3 September: 10.8 µg/m³Prince Albert, 4 September: 11.5 µg/m³Prince Albert, 5 September: 7.8 µg/m³Prince Albert, 6 September: 10.7 µg/m³Prince Albert, 7 September: 10.4 µg/m³Prince Albert, 8 September: 24.4 µg/m³Prince Albert, 9 September: 24.2 µg/m³Prince Albert, 10 September: 24.1 µg/m³Prince Albert, 11 September: 36.2 µg/m³, 3.4× its usual 10.8Prince Albert, 12 September: 18.1 µg/m³Prince Albert, 13 September: 11.1 µg/m³Prince Albert, 14 September: 6.8 µg/m³Prince Albert, 15 September: 6.5 µg/m³Prince Albert, 16 September: 20.5 µg/m³Flin FlonFlin Flon, 3 September: no readingFlin Flon, 4 September: no readingFlin Flon, 5 September: no readingFlin Flon, 6 September: no readingFlin Flon, 7 September: no readingFlin Flon, 8 September: no readingFlin Flon, 9 September: no readingFlin Flon, 10 September: no readingFlin Flon, 11 September: 30.1 µg/m³, 2.2× its usual 13.4Flin Flon, 12 September: no readingFlin Flon, 13 September: 12.6 µg/m³Flin Flon, 14 September: no readingFlin Flon, 15 September: 10.3 µg/m³Flin Flon, 16 September: no readingSaskatoonSaskatoon, 3 September: no readingSaskatoon, 4 September: 14.4 µg/m³Saskatoon, 5 September: 6.0 µg/m³Saskatoon, 6 September: 9.4 µg/m³Saskatoon, 7 September: 11.0 µg/m³Saskatoon, 8 September: 29.8 µg/m³Saskatoon, 9 September: 31.6 µg/m³Saskatoon, 10 September: 22.2 µg/m³Saskatoon, 11 September: 25.0 µg/m³, 2.8× its usual 8.8Saskatoon, 12 September: 31.9 µg/m³Saskatoon, 13 September: 7.4 µg/m³Saskatoon, 14 September: 5.3 µg/m³Saskatoon, 15 September: 8.4 µg/m³Saskatoon, 16 September: 16.1 µg/m³3 Sep579111315
Every counted city, 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
EphrataWashington, United States3 103.06 September6.316×
WenatcheeWashington, United States1 83.36 September5.216×
Williams LakeBritish Columbia, Canada5 77.08 September3.815×
WhistlerBritish Columbia, Canada1 65.56 September4.313×
Grande PrairieAlberta, Canada6 67.912 September6.311×
QuincyWashington, United States1 58.86 September5.611×
CranbrookBritish Columbia, Canada3 56.27 September6.48.8×
QuesnelBritish Columbia, Canada7 68.28 September8.38.2×
Tri-CitiesWashington, United States1 40.26 September4.78.0×
EllensburgWashington, United States1 41.36 September5.27.9×
MeadWashington, United States1 41.06 September5.27.9×
CrestonBritish Columbia, Canada3 44.06 September5.87.6×
SquamishBritish Columbia, Canada1 49.36 September6.67.5×
CastlegarBritish Columbia, Canada3 56.17 September7.67.4×
EdsonAlberta, Canada4 45.412 September6.17.4×
SmithersBritish Columbia, Canada1 37.16 September4.47.4×
HopeBritish Columbia, Canada1 43.16 September6.07.2×
SandpointIdaho, United States2 50.56 September7.66.6×
SpokaneWashington, United States1 43.56 September6.66.6×
Airway HeightsWashington, United States1 42.36 September6.46.6×
Spokane ValleyWashington, United States1 39.06 September6.06.5×
MissoulaMontana, United States2 33.46 September5.36.3×
ProsserWashington, United States1 40.66 September6.56.2×
YakimaWashington, United States1 37.76 September6.16.2×
Fort St. JohnBritish Columbia, Canada3 37.57 September6.16.1×
ButteMontana, United States2 31.96 September5.26.1×
ToppenishWashington, United States1 44.86 September7.56.0×
Prince GeorgeBritish Columbia, Canada7 49.87 September8.75.7×
West VancouverBritish Columbia, Canada1 28.16 September4.95.6×
LethbridgeAlberta, Canada2 39.57 September7.25.5×
Columbia FallsMontana, United States2 38.07 September6.95.5×
Coeur d'AleneIdaho, United States1 36.86 September6.95.3×
PullmanWashington, United States1 31.46 September5.95.3×
SunnysideWashington, United States1 39.86 September7.65.2×
KelownaBritish Columbia, Canada2 37.77 September7.35.2×
GibsonsBritish Columbia, Canada1 31.26 September6.15.1×
HermistonOregon, United States1 29.36 September5.85.1×
VernonBritish Columbia, Canada2 38.46 September8.04.8×
St. AlbertAlberta, Canada4 36.49 September7.64.8×
Walla WallaWashington, United States1 26.36 September5.74.6×
Drayton ValleyAlberta, Canada1 34.89 September7.84.5×
Sherwood ParkAlberta, Canada4 34.69 September7.84.4×
AgassizBritish Columbia, Canada1 27.56 September6.34.4×
Grand CentreAlberta, Canada2 31.911 September7.64.2×
EdmontonAlberta, Canada6 45.19 September11.04.1×
LewistonIdaho, United States1 34.86 September8.54.1×
MoscowIdaho, United States1 29.16 September7.24.0×
Fort SaskatchewanAlberta, Canada4 36.19 September9.23.9×
KamloopsBritish Columbia, Canada2 33.97 September8.83.9×
HelenaMontana, United States1 29.87 September7.73.9×
Helena Valley West CentralMontana, United States1 29.87 September7.73.9×
Prince AlbertSaskatchewan, Canada1 36.211 September10.83.4×
CalgaryAlberta, Canada5 33.77 September9.83.4×
Red DeerAlberta, Canada3 30.59 September9.03.4×
SaskatoonSaskatchewan, Canada1 25.011 September8.82.8×
Great FallsMontana, United States1 30.67 September11.32.7×
Flin FlonManitoba, Canada1 30.111 September13.42.2×

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 Canada and the United States

Number 28 of 173 episodes in Canada and the United States 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, North-western Canada and United States, September 2025: 57 cities with PM2.5 at twice their usual or more, 6 to 13 September 2025, smogrank.com/episodes/2025-09-north-western-canada-and-united-states (accessed 5 October 2026).

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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.