SmogRank / Episodes / United States

North-western United States and Canada, 1 to 10 September 2025

For 10 days, from 1 to 10 September 2025, 54 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Squamish, British Columbia, Canada: 173.0 µg/m³ on 3 September, about 25× its usual 7.0.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached54in 2 countries
Days101 to 10 September 2025
Worst day5 September30 cities counted
Furthest above usual25×Squamish

Day by day

5 September 30 cities at twice their usual or more
PendletonPocatelloCondaThe DallesSheridanBellevueRentonAuburnPicnic Point-North LynnwoodColumbia CityMount VernonRedmondSeattleBurienBellinghamTacomaParklandBendAnacortesOak HarborLangleyBremertonLaceyGreshamDeltaSalmon CreekVancouverCentraliaRichmondOregon CityMilwaukiePortlandPrince AlbertLongviewCanbyGilletteTigardBeavertonVictoriaCasperPort AngelesHillsboroWoodburnLangfordForest GroveNorth CowichanDuncanSalemMcMinnvilleAlbanyAberdeenNanaimoHarewoodDallasCorvallisEugenePrince GeorgeRoseburgCoos BayRapid CitySaskatoonGreat FallsReginaHelenaKamloopsMoses LakeLewistonRexburgNampaBozemanWalla WallaBillingsChilliwackMoscowMeridianAbbotsfordVernonHermistonAirdrieCoeur d'AleneKelownaBoisePullmanSunnysideIdaho FallsShorelinePort CoquitlamButteRed DeerMissionMissoulaVancouverStrawberry HillSwift CurrentSpokane ValleySpokaneMedicine HatNorth VancouverBurnabyCoquitlamInglewood-Finn HillKirklandEllensburgTri-CitiesCranbrookYakimaLethbridgeCalgaryEdmontonSt. AlbertSherwood ParkWenatcheeWest VancouverSquamish
29 Aug30311 Sep2345678910111213
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

EdmontonEdmonton, 29 August: 27.1 µg/m³Edmonton, 30 August: 18.4 µg/m³Edmonton, 31 August: 76.6 µg/m³Edmonton, 1 September: 140.0 µg/m³, 12× its usual 11.4Edmonton, 2 September: 46.6 µg/m³, 4.1× its usual 11.4Edmonton, 3 September: 48.2 µg/m³, 4.3× its usual 11.3Edmonton, 4 September: 36.8 µg/m³, 3.3× its usual 11.3Edmonton, 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/m³Edmonton, 12 September: 25.3 µg/m³Edmonton, 13 September: 22.0 µg/m³Sherwood ParkSherwood Park, 29 August: 19.2 µg/m³Sherwood Park, 30 August: 10.1 µg/m³Sherwood Park, 31 August: 58.0 µg/m³Sherwood Park, 1 September: 126.0 µg/m³, 16× its usual 8.0Sherwood Park, 2 September: 41.9 µg/m³, 5.2× its usual 8.0Sherwood Park, 3 September: 42.7 µg/m³, 5.4× its usual 7.9Sherwood Park, 4 September: 32.7 µg/m³, 4.1× its usual 8.0Sherwood 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/m³St. AlbertSt. Albert, 29 August: 21.5 µg/m³St. Albert, 30 August: 16.0 µg/m³St. Albert, 31 August: 52.9 µg/m³St. Albert, 1 September: 126.0 µg/m³, 15× its usual 8.2St. Albert, 2 September: 42.4 µg/m³, 5.2× its usual 8.2St. Albert, 3 September: 44.2 µg/m³, 5.5× its usual 8.1St. Albert, 4 September: 33.6 µg/m³, 4.1× its usual 8.2St. 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/m³St. Albert, 13 September: 19.3 µg/m³Red DeerRed Deer, 29 August: 14.0 µg/m³Red Deer, 30 August: 10.9 µg/m³Red Deer, 31 August: 10.7 µg/m³Red Deer, 1 September: 54.1 µg/m³, 5.7× its usual 9.5Red Deer, 2 September: 58.6 µg/m³, 6.2× its usual 9.4Red Deer, 3 September: 46.8 µg/m³, 5.0× its usual 9.4Red Deer, 4 September: 35.7 µg/m³, 3.8× its usual 9.5Red 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/m³CalgaryCalgary, 29 August: 12.7 µg/m³Calgary, 30 August: 12.5 µg/m³Calgary, 31 August: 12.9 µg/m³Calgary, 1 September: 20.2 µg/m³Calgary, 2 September: 100.3 µg/m³, 9.9× its usual 10.1Calgary, 3 September: 57.2 µg/m³, 5.7× its usual 10.1Calgary, 4 September: 47.8 µg/m³, 4.6× its usual 10.3Calgary, 5 September: 37.0 µg/m³, 3.7× its usual 10.1Calgary, 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/m³LethbridgeLethbridge, 29 August: 7.9 µg/m³Lethbridge, 30 August: 8.3 µg/m³Lethbridge, 31 August: 11.4 µg/m³Lethbridge, 1 September: 20.7 µg/m³Lethbridge, 2 September: 72.8 µg/m³, 9.2× its usual 7.9Lethbridge, 3 September: 62.0 µg/m³, 7.8× its usual 7.9Lethbridge, 4 September: 40.9 µg/m³, 5.1× its usual 8.0Lethbridge, 5 September: 30.6 µg/m³, 3.9× its usual 7.9Lethbridge, 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/m³Swift CurrentSwift Current, 29 August: 7.3 µg/m³Swift Current, 30 August: 6.0 µg/m³Swift Current, 31 August: 6.3 µg/m³Swift Current, 1 September: 37.5 µg/m³Swift Current, 2 September: 53.4 µg/m³, 6.5× its usual 8.2Swift Current, 3 September: 19.7 µg/m³Swift Current, 4 September: 26.2 µg/m³, 3.2× its usual 8.2Swift Current, 5 September: 8.0 µg/m³Swift Current, 6 September: 5.6 µg/m³Swift Current, 7 September: 8.8 µg/m³Swift Current, 8 September: 19.3 µg/m³Swift Current, 9 September: 20.1 µg/m³Swift Current, 10 September: 16.8 µg/m³Swift Current, 11 September: 17.1 µg/m³Swift Current, 12 September: 18.1 µg/m³Swift Current, 13 September: 7.0 µg/m³Medicine HatMedicine Hat, 29 August: 7.0 µg/m³Medicine Hat, 30 August: 8.7 µg/m³Medicine Hat, 31 August: 9.9 µg/m³Medicine Hat, 1 September: 14.4 µg/m³Medicine Hat, 2 September: 48.0 µg/m³, 6.7× its usual 7.2Medicine Hat, 3 September: 33.8 µg/m³, 4.7× its usual 7.2Medicine Hat, 4 September: 27.5 µg/m³, 3.9× its usual 7.1Medicine Hat, 5 September: 10.4 µg/m³Medicine Hat, 6 September: 6.9 µg/m³Medicine Hat, 7 September: 16.8 µg/m³Medicine Hat, 8 September: 18.6 µg/m³Medicine Hat, 9 September: 19.8 µg/m³Medicine Hat, 10 September: 15.9 µg/m³Medicine Hat, 11 September: 14.8 µg/m³Medicine Hat, 12 September: 12.8 µg/m³Medicine Hat, 13 September: 6.7 µg/m³ReginaRegina, 29 August: 17.0 µg/m³Regina, 30 August: 13.9 µg/m³Regina, 31 August: 10.5 µg/m³Regina, 1 September: 24.5 µg/m³Regina, 2 September: 33.9 µg/m³, 3.3× its usual 10.2Regina, 3 September: 11.0 µg/m³Regina, 4 September: 10.2 µg/m³Regina, 5 September: 4.6 µg/m³Regina, 6 September: 11.0 µg/m³Regina, 7 September: 8.0 µg/m³Regina, 8 September: 15.8 µg/m³Regina, 9 September: 22.8 µg/m³Regina, 10 September: 16.5 µg/m³Regina, 11 September: 15.0 µg/m³Regina, 12 September: 11.9 µg/m³Regina, 13 September: 5.6 µg/m³SaskatoonSaskatoon, 29 August: 16.3 µg/m³Saskatoon, 30 August: 9.3 µg/m³Saskatoon, 31 August: 8.3 µg/m³Saskatoon, 1 September: 55.3 µg/m³Saskatoon, 2 September: 26.0 µg/m³, 2.5× its usual 10.5Saskatoon, 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/m³Saskatoon, 12 September: 31.9 µg/m³Saskatoon, 13 September: 7.4 µg/m³SquamishSquamish, 29 August: 15.9 µg/m³Squamish, 30 August: 13.2 µg/m³Squamish, 31 August: 20.9 µg/m³Squamish, 1 September: 12.1 µg/m³Squamish, 2 September: 17.0 µg/m³Squamish, 3 September: 173.0 µg/m³, 25× its usual 7.0Squamish, 4 September: 53.1 µg/m³, 7.6× its usual 7.0Squamish, 5 September: 43.1 µg/m³, 6.3× its usual 6.8Squamish, 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/m³West VancouverWest Vancouver, 29 August: 14.3 µg/m³West Vancouver, 30 August: 8.8 µg/m³West Vancouver, 31 August: 12.9 µg/m³West Vancouver, 1 September: 8.3 µg/m³West Vancouver, 2 September: 9.7 µg/m³West Vancouver, 3 September: 87.2 µg/m³, 17× its usual 5.2West Vancouver, 4 September: 21.8 µg/m³West Vancouver, 5 September: 31.4 µg/m³, 6.3× its usual 4.9West 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/m³CoquitlamCoquitlam, 29 August: 12.8 µg/m³Coquitlam, 30 August: 8.7 µg/m³Coquitlam, 31 August: 11.0 µg/m³Coquitlam, 1 September: 8.7 µg/m³Coquitlam, 2 September: 11.9 µg/m³Coquitlam, 3 September: 40.1 µg/m³, 7.4× its usual 5.4Coquitlam, 4 September: 21.5 µg/m³Coquitlam, 5 September: 21.9 µg/m³Coquitlam, 6 September: 16.6 µg/m³Coquitlam, 7 September: 7.1 µg/m³Coquitlam, 8 September: 6.8 µg/m³Coquitlam, 9 September: 8.0 µg/m³Coquitlam, 10 September: 5.6 µg/m³Coquitlam, 11 September: 7.3 µg/m³Coquitlam, 12 September: 4.8 µg/m³Coquitlam, 13 September: 5.6 µg/m³BurnabyBurnaby, 29 August: 14.4 µg/m³Burnaby, 30 August: 8.4 µg/m³Burnaby, 31 August: 10.8 µg/m³Burnaby, 1 September: 8.0 µg/m³Burnaby, 2 September: 12.1 µg/m³Burnaby, 3 September: 37.5 µg/m³, 6.9× its usual 5.4Burnaby, 4 September: 11.7 µg/m³Burnaby, 5 September: 18.1 µg/m³Burnaby, 6 September: 13.7 µg/m³Burnaby, 7 September: 7.1 µg/m³Burnaby, 8 September: 6.6 µg/m³Burnaby, 9 September: 8.3 µg/m³Burnaby, 10 September: 5.1 µg/m³Burnaby, 11 September: 7.3 µg/m³Burnaby, 12 September: 4.9 µg/m³Burnaby, 13 September: 5.6 µg/m³North VancouverNorth Vancouver, 29 August: 11.3 µg/m³North Vancouver, 30 August: 7.1 µg/m³North Vancouver, 31 August: 10.5 µg/m³North Vancouver, 1 September: 7.8 µg/m³North Vancouver, 2 September: 8.5 µg/m³North Vancouver, 3 September: 35.1 µg/m³, 6.9× its usual 5.1North Vancouver, 4 September: 17.8 µg/m³North Vancouver, 5 September: 23.2 µg/m³North Vancouver, 6 September: 18.0 µg/m³North Vancouver, 7 September: 7.1 µg/m³North Vancouver, 8 September: 5.4 µg/m³North Vancouver, 9 September: 6.4 µg/m³North Vancouver, 10 September: 4.7 µg/m³North Vancouver, 11 September: 7.2 µg/m³North Vancouver, 12 September: 5.4 µg/m³North Vancouver, 13 September: 5.1 µg/m³Strawberry HillStrawberry Hill, 29 August: 11.4 µg/m³Strawberry Hill, 30 August: 7.4 µg/m³Strawberry Hill, 31 August: 10.3 µg/m³Strawberry Hill, 1 September: 7.1 µg/m³Strawberry Hill, 2 September: 10.5 µg/m³Strawberry Hill, 3 September: 34.8 µg/m³, 6.4× its usual 5.4Strawberry Hill, 4 September: 11.8 µg/m³Strawberry Hill, 5 September: 18.2 µg/m³Strawberry Hill, 6 September: 10.7 µg/m³Strawberry Hill, 7 September: 6.3 µg/m³Strawberry Hill, 8 September: 6.1 µg/m³Strawberry Hill, 9 September: 8.5 µg/m³Strawberry Hill, 10 September: 4.7 µg/m³Strawberry Hill, 11 September: 6.1 µg/m³Strawberry Hill, 12 September: 4.4 µg/m³Strawberry Hill, 13 September: 5.3 µg/m³VancouverVancouver, 29 August: 14.5 µg/m³Vancouver, 30 August: 8.5 µg/m³Vancouver, 31 August: 11.4 µg/m³Vancouver, 1 September: 8.7 µg/m³Vancouver, 2 September: 9.6 µg/m³Vancouver, 3 September: 34.5 µg/m³, 6.4× its usual 5.4Vancouver, 4 September: 12.4 µg/m³Vancouver, 5 September: 21.5 µg/m³Vancouver, 6 September: 13.6 µg/m³Vancouver, 7 September: 7.7 µg/m³Vancouver, 8 September: 6.6 µg/m³Vancouver, 9 September: 7.4 µg/m³Vancouver, 10 September: 4.7 µg/m³Vancouver, 11 September: 7.2 µg/m³Vancouver, 12 September: 5.5 µg/m³Vancouver, 13 September: 6.9 µg/m³Great FallsGreat Falls, 29 August: 10.2 µg/m³Great Falls, 30 August: 8.7 µg/m³Great Falls, 31 August: 15.6 µg/m³Great Falls, 1 September: 17.1 µg/m³Great Falls, 2 September: 20.5 µg/m³Great Falls, 3 September: 33.0 µg/m³, 2.8× its usual 11.6Great Falls, 4 September: 29.7 µg/m³, 2.6× its usual 11.6Great 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/m³MissionMission, 29 August: 14.0 µg/m³Mission, 30 August: 10.0 µg/m³Mission, 31 August: 11.6 µg/m³Mission, 1 September: 10.9 µg/m³Mission, 2 September: 12.6 µg/m³Mission, 3 September: 32.3 µg/m³, 6.3× its usual 5.1Mission, 4 September: 26.9 µg/m³, 5.3× its usual 5.1Mission, 5 September: 29.6 µg/m³, 5.8× its usual 5.1Mission, 6 September: 18.7 µg/m³Mission, 7 September: 7.3 µg/m³Mission, 8 September: 7.6 µg/m³Mission, 9 September: 11.8 µg/m³Mission, 10 September: 8.0 µg/m³Mission, 11 September: 8.3 µg/m³Mission, 12 September: 4.7 µg/m³Mission, 13 September: 5.8 µg/m³ChilliwackChilliwack, 29 August: 14.6 µg/m³Chilliwack, 30 August: 10.7 µg/m³Chilliwack, 31 August: 12.6 µg/m³Chilliwack, 1 September: 11.7 µg/m³Chilliwack, 2 September: 13.4 µg/m³Chilliwack, 3 September: 31.3 µg/m³, 4.7× its usual 6.6Chilliwack, 4 September: 25.2 µg/m³, 4.0× its usual 6.3Chilliwack, 5 September: 28.9 µg/m³, 4.7× its usual 6.1Chilliwack, 6 September: 16.0 µg/m³Chilliwack, 7 September: 8.2 µg/m³Chilliwack, 8 September: 8.7 µg/m³Chilliwack, 9 September: 10.6 µg/m³Chilliwack, 10 September: 9.4 µg/m³Chilliwack, 11 September: 8.6 µg/m³Chilliwack, 12 September: 6.4 µg/m³Chilliwack, 13 September: 6.3 µg/m³BillingsBillings, 29 August: 5.1 µg/m³Billings, 30 August: 6.8 µg/m³Billings, 31 August: 7.7 µg/m³Billings, 1 September: 11.4 µg/m³Billings, 2 September: 12.3 µg/m³Billings, 3 September: 31.1 µg/m³, 4.6× its usual 6.7Billings, 4 September: 26.2 µg/m³, 3.9× its usual 6.7Billings, 5 September: 12.4 µg/m³Billings, 6 September: 11.1 µg/m³Billings, 7 September: 13.1 µg/m³Billings, 8 September: 12.6 µg/m³Billings, 9 September: 16.3 µg/m³Billings, 10 September: 7.6 µg/m³Billings, 11 September: no readingBillings, 12 September: no readingBillings, 13 September: 4.1 µg/m³Port CoquitlamPort Coquitlam, 29 August: 12.5 µg/m³Port Coquitlam, 30 August: 9.0 µg/m³Port Coquitlam, 31 August: 10.0 µg/m³Port Coquitlam, 1 September: 8.3 µg/m³Port Coquitlam, 2 September: 10.1 µg/m³Port Coquitlam, 3 September: 31.0 µg/m³, 6.1× its usual 5.1Port Coquitlam, 4 September: 16.7 µg/m³Port Coquitlam, 5 September: 20.5 µg/m³Port Coquitlam, 6 September: 16.2 µg/m³Port Coquitlam, 7 September: 6.5 µg/m³Port Coquitlam, 8 September: 7.4 µg/m³Port Coquitlam, 9 September: 8.5 µg/m³Port Coquitlam, 10 September: 6.0 µg/m³Port Coquitlam, 11 September: 6.6 µg/m³Port Coquitlam, 12 September: 4.3 µg/m³Port Coquitlam, 13 September: 4.8 µg/m³SpokaneSpokane, 29 August: 11.9 µg/m³Spokane, 30 August: 15.0 µg/m³Spokane, 31 August: 18.9 µg/m³Spokane, 1 September: 15.2 µg/m³Spokane, 2 September: 19.2 µg/m³Spokane, 3 September: 30.0 µg/m³, 4.3× its usual 7.0Spokane, 4 September: 31.6 µg/m³, 4.6× its usual 6.8Spokane, 5 September: 37.7 µg/m³, 5.7× its usual 6.6Spokane, 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/m³AbbotsfordAbbotsford, 29 August: 12.7 µg/m³Abbotsford, 30 August: 9.7 µg/m³Abbotsford, 31 August: 11.6 µg/m³Abbotsford, 1 September: 11.1 µg/m³Abbotsford, 2 September: 11.9 µg/m³Abbotsford, 3 September: 29.7 µg/m³, 5.0× its usual 6.0Abbotsford, 4 September: 17.3 µg/m³Abbotsford, 5 September: 22.2 µg/m³Abbotsford, 6 September: 12.0 µg/m³Abbotsford, 7 September: 7.1 µg/m³Abbotsford, 8 September: 7.9 µg/m³Abbotsford, 9 September: 10.0 µg/m³Abbotsford, 10 September: 7.8 µg/m³Abbotsford, 11 September: 7.8 µg/m³Abbotsford, 12 September: 6.1 µg/m³Abbotsford, 13 September: 7.9 µg/m³Inglewood-Finn HillInglewood-Finn Hill, 29 August: 19.1 µg/m³Inglewood-Finn Hill, 30 August: 13.7 µg/m³Inglewood-Finn Hill, 31 August: 16.4 µg/m³Inglewood-Finn Hill, 1 September: 12.3 µg/m³Inglewood-Finn Hill, 2 September: 16.1 µg/m³Inglewood-Finn Hill, 3 September: 27.0 µg/m³, 5.4× its usual 4.1Inglewood-Finn Hill, 4 September: 20.9 µg/m³Inglewood-Finn Hill, 5 September: 37.5 µg/m³, 7.5× its usual 4.1Inglewood-Finn Hill, 6 September: 17.7 µg/m³Inglewood-Finn Hill, 7 September: 5.1 µg/m³Inglewood-Finn Hill, 8 September: 7.7 µg/m³Inglewood-Finn Hill, 9 September: 9.3 µg/m³Inglewood-Finn Hill, 10 September: 9.7 µg/m³Inglewood-Finn Hill, 11 September: 13.8 µg/m³Inglewood-Finn Hill, 12 September: 5.9 µg/m³Inglewood-Finn Hill, 13 September: 5.3 µg/m³Spokane ValleySpokane Valley, 29 August: 10.2 µg/m³Spokane Valley, 30 August: 14.6 µg/m³Spokane Valley, 31 August: 17.0 µg/m³Spokane Valley, 1 September: 14.0 µg/m³Spokane Valley, 2 September: 16.4 µg/m³Spokane Valley, 3 September: 26.6 µg/m³, 4.2× its usual 6.4Spokane Valley, 4 September: 29.5 µg/m³, 4.7× its usual 6.3Spokane Valley, 5 September: 37.2 µg/m³, 6.1× its usual 6.1Spokane Valley, 6 September: 39.0 µg/m³, 6.6× its usual 5.9Spokane 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/m³SunnysideSunnyside, 29 August: 13.5 µg/m³Sunnyside, 30 August: 13.8 µg/m³Sunnyside, 31 August: 12.9 µg/m³Sunnyside, 1 September: 17.8 µg/m³Sunnyside, 2 September: 18.7 µg/m³Sunnyside, 3 September: 25.9 µg/m³, 3.5× its usual 7.3Sunnyside, 4 September: no readingSunnyside, 5 September: no readingSunnyside, 6 September: 39.8 µg/m³, 5.8× its usual 6.9Sunnyside, 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/m³KirklandKirkland, 29 August: 18.0 µg/m³Kirkland, 30 August: 12.5 µg/m³Kirkland, 31 August: 15.0 µg/m³Kirkland, 1 September: 12.4 µg/m³Kirkland, 2 September: 14.7 µg/m³Kirkland, 3 September: 25.4 µg/m³, 5.1× its usual 3.8Kirkland, 4 September: 20.0 µg/m³Kirkland, 5 September: 38.8 µg/m³, 7.8× its usual 3.5Kirkland, 6 September: 16.1 µg/m³Kirkland, 7 September: 4.4 µg/m³Kirkland, 8 September: 6.5 µg/m³Kirkland, 9 September: 8.2 µg/m³Kirkland, 10 September: 9.1 µg/m³Kirkland, 11 September: 12.6 µg/m³Kirkland, 12 September: 5.3 µg/m³Kirkland, 13 September: 4.4 µg/m³HelenaHelena, 29 August: no readingHelena, 30 August: no readingHelena, 31 August: no readingHelena, 1 September: no readingHelena, 2 September: no readingHelena, 3 September: 25.3 µg/m³, 3.3× its usual 7.6Helena, 4 September: 27.9 µg/m³, 3.6× its usual 7.7Helena, 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/m³Moses LakeMoses Lake, 29 August: 12.7 µg/m³Moses Lake, 30 August: 12.8 µg/m³Moses Lake, 31 August: 17.6 µg/m³Moses Lake, 1 September: 15.5 µg/m³Moses Lake, 2 September: 31.9 µg/m³Moses Lake, 3 September: 25.1 µg/m³, 3.7× its usual 6.8Moses Lake, 4 September: 26.5 µg/m³, 4.0× its usual 6.7Moses Lake, 5 September: no readingMoses Lake, 6 September: no readingMoses Lake, 7 September: no readingMoses Lake, 8 September: no readingMoses Lake, 9 September: 8.6 µg/m³Moses Lake, 10 September: 16.5 µg/m³Moses Lake, 11 September: 14.6 µg/m³Moses Lake, 12 September: 13.8 µg/m³Moses Lake, 13 September: 13.6 µg/m³YakimaYakima, 29 August: 12.3 µg/m³Yakima, 30 August: 9.8 µg/m³Yakima, 31 August: 9.2 µg/m³Yakima, 1 September: 18.0 µg/m³Yakima, 2 September: 20.1 µg/m³Yakima, 3 September: 20.7 µg/m³Yakima, 4 September: 58.0 µg/m³, 9.1× its usual 6.4Yakima, 5 September: 44.7 µg/m³, 7.2× its usual 6.2Yakima, 6 September: 37.7 µg/m³, 6.1× its usual 6.2Yakima, 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/m³AirdrieAirdrie, 29 August: no readingAirdrie, 30 August: no readingAirdrie, 31 August: no readingAirdrie, 1 September: no readingAirdrie, 2 September: no readingAirdrie, 3 September: no readingAirdrie, 4 September: 41.9 µg/m³, 5.3× its usual 7.9Airdrie, 5 September: no readingAirdrie, 6 September: no readingAirdrie, 7 September: no readingAirdrie, 8 September: no readingAirdrie, 9 September: no readingAirdrie, 10 September: no readingAirdrie, 11 September: no readingAirdrie, 12 September: no readingAirdrie, 13 September: no readingWenatcheeWenatchee, 29 August: 11.4 µg/m³Wenatchee, 30 August: 10.6 µg/m³Wenatchee, 31 August: 10.9 µg/m³Wenatchee, 1 September: 16.8 µg/m³Wenatchee, 2 September: 21.5 µg/m³Wenatchee, 3 September: 20.3 µg/m³Wenatchee, 4 September: 36.2 µg/m³, 6.5× its usual 5.6Wenatchee, 5 September: 58.2 µg/m³, 11× its usual 5.4Wenatchee, 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/m³KamloopsKamloops, 29 August: 9.4 µg/m³Kamloops, 30 August: 10.7 µg/m³Kamloops, 31 August: 11.4 µg/m³Kamloops, 1 September: 9.8 µg/m³Kamloops, 2 September: 15.4 µg/m³Kamloops, 3 September: 18.6 µg/m³Kamloops, 4 September: 33.3 µg/m³, 3.5× its usual 9.6Kamloops, 5 September: 29.2 µg/m³, 3.1× its usual 9.4Kamloops, 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/m³Coeur d'AleneCoeur d'Alene, 29 August: 10.5 µg/m³Coeur d'Alene, 30 August: 13.9 µg/m³Coeur d'Alene, 31 August: 19.0 µg/m³Coeur d'Alene, 1 September: 14.8 µg/m³Coeur d'Alene, 2 September: 15.1 µg/m³Coeur d'Alene, 3 September: 24.8 µg/m³Coeur d'Alene, 4 September: 29.8 µg/m³, 4.2× its usual 7.1Coeur d'Alene, 5 September: 37.7 µg/m³, 5.4× its usual 7.0Coeur 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/m³MissoulaMissoula, 29 August: 9.0 µg/m³Missoula, 30 August: 9.0 µg/m³Missoula, 31 August: 17.7 µg/m³Missoula, 1 September: 10.3 µg/m³Missoula, 2 September: 11.8 µg/m³Missoula, 3 September: 16.2 µg/m³Missoula, 4 September: 27.6 µg/m³, 5.1× its usual 5.4Missoula, 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/m³VernonVernon, 29 August: 12.8 µg/m³Vernon, 30 August: 7.0 µg/m³Vernon, 31 August: 7.3 µg/m³Vernon, 1 September: 12.7 µg/m³Vernon, 2 September: 15.0 µg/m³Vernon, 3 September: 18.8 µg/m³Vernon, 4 September: 27.5 µg/m³, 3.2× its usual 8.6Vernon, 5 September: 42.4 µg/m³, 5.1× its usual 8.3Vernon, 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/m³BozemanBozeman, 29 August: 8.7 µg/m³Bozeman, 30 August: 8.0 µg/m³Bozeman, 31 August: 9.9 µg/m³Bozeman, 1 September: 11.0 µg/m³Bozeman, 2 September: 12.1 µg/m³Bozeman, 3 September: 15.3 µg/m³Bozeman, 4 September: 26.2 µg/m³, 4.5× its usual 5.8Bozeman, 5 September: 15.8 µg/m³Bozeman, 6 September: 22.1 µg/m³Bozeman, 7 September: 18.7 µg/m³Bozeman, 8 September: 7.2 µg/m³Bozeman, 9 September: 9.8 µg/m³Bozeman, 10 September: 7.7 µg/m³Bozeman, 11 September: 7.6 µg/m³Bozeman, 12 September: 5.0 µg/m³Bozeman, 13 September: 5.2 µg/m³CranbrookCranbrook, 29 August: 11.9 µg/m³Cranbrook, 30 August: 9.9 µg/m³Cranbrook, 31 August: 14.3 µg/m³Cranbrook, 1 September: 14.9 µg/m³Cranbrook, 2 September: 15.1 µg/m³Cranbrook, 3 September: 16.3 µg/m³Cranbrook, 4 September: 25.4 µg/m³, 3.7× its usual 6.8Cranbrook, 5 September: 25.5 µg/m³, 3.8× its usual 6.7Cranbrook, 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/m³KelownaKelowna, 29 August: 9.2 µg/m³Kelowna, 30 August: 6.9 µg/m³Kelowna, 31 August: 9.4 µg/m³Kelowna, 1 September: 13.0 µg/m³Kelowna, 2 September: 16.8 µg/m³Kelowna, 3 September: 17.1 µg/m³Kelowna, 4 September: 23.2 µg/m³Kelowna, 5 September: 42.7 µg/m³, 5.4× its usual 7.9Kelowna, 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/m³EllensburgEllensburg, 29 August: 11.3 µg/m³Ellensburg, 30 August: 9.3 µg/m³Ellensburg, 31 August: 8.5 µg/m³Ellensburg, 1 September: 11.1 µg/m³Ellensburg, 2 September: 11.5 µg/m³Ellensburg, 3 September: 14.8 µg/m³Ellensburg, 4 September: 23.7 µg/m³Ellensburg, 5 September: 40.1 µg/m³, 7.6× its usual 5.3Ellensburg, 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/m³LewistonLewiston, 29 August: 14.1 µg/m³Lewiston, 30 August: 14.7 µg/m³Lewiston, 31 August: 18.3 µg/m³Lewiston, 1 September: 13.8 µg/m³Lewiston, 2 September: 15.1 µg/m³Lewiston, 3 September: 14.8 µg/m³Lewiston, 4 September: 17.7 µg/m³Lewiston, 5 September: 35.1 µg/m³, 4.1× its usual 8.6Lewiston, 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/m³Tri-CitiesTri-Cities, 29 August: no readingTri-Cities, 30 August: no readingTri-Cities, 31 August: no readingTri-Cities, 1 September: no readingTri-Cities, 2 September: no readingTri-Cities, 3 September: 19.8 µg/m³Tri-Cities, 4 September: 19.8 µg/m³Tri-Cities, 5 September: 34.8 µg/m³, 7.0× its usual 4.8Tri-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/m³MoscowMoscow, 29 August: 12.1 µg/m³Moscow, 30 August: 15.0 µg/m³Moscow, 31 August: 17.4 µg/m³Moscow, 1 September: 13.7 µg/m³Moscow, 2 September: 18.5 µg/m³Moscow, 3 September: 18.1 µg/m³Moscow, 4 September: 18.8 µg/m³Moscow, 5 September: 34.5 µg/m³, 4.7× its usual 7.3Moscow, 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/m³PullmanPullman, 29 August: 12.2 µg/m³Pullman, 30 August: 14.2 µg/m³Pullman, 31 August: 17.1 µg/m³Pullman, 1 September: 13.2 µg/m³Pullman, 2 September: 17.3 µg/m³Pullman, 3 September: 14.7 µg/m³Pullman, 4 September: 15.8 µg/m³Pullman, 5 September: 34.2 µg/m³, 5.6× its usual 6.1Pullman, 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/m³ShorelineShoreline, 29 August: 12.6 µg/m³Shoreline, 30 August: 10.0 µg/m³Shoreline, 31 August: 10.9 µg/m³Shoreline, 1 September: 10.3 µg/m³Shoreline, 2 September: 10.2 µg/m³Shoreline, 3 September: 16.6 µg/m³Shoreline, 4 September: 12.2 µg/m³Shoreline, 5 September: 33.7 µg/m³, 6.0× its usual 5.6Shoreline, 6 September: 11.4 µg/m³Shoreline, 7 September: 5.9 µg/m³Shoreline, 8 September: 6.6 µg/m³Shoreline, 9 September: 8.1 µg/m³Shoreline, 10 September: 7.9 µg/m³Shoreline, 11 September: 10.3 µg/m³Shoreline, 12 September: 6.7 µg/m³Shoreline, 13 September: 5.7 µg/m³HermistonHermiston, 29 August: 20.5 µg/m³Hermiston, 30 August: 14.0 µg/m³Hermiston, 31 August: 12.9 µg/m³Hermiston, 1 September: 13.2 µg/m³Hermiston, 2 September: 16.3 µg/m³Hermiston, 3 September: 18.0 µg/m³Hermiston, 4 September: 18.5 µg/m³Hermiston, 5 September: 31.4 µg/m³, 5.2× its usual 6.0Hermiston, 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/m³NampaNampa, 29 August: 10.3 µg/m³Nampa, 30 August: 11.8 µg/m³Nampa, 31 August: 9.5 µg/m³Nampa, 1 September: 12.3 µg/m³Nampa, 2 September: 10.9 µg/m³Nampa, 3 September: 12.7 µg/m³Nampa, 4 September: 17.7 µg/m³Nampa, 5 September: 30.5 µg/m³, 4.3× its usual 7.1Nampa, 6 September: 16.3 µg/m³Nampa, 7 September: 9.9 µg/m³Nampa, 8 September: 8.8 µg/m³Nampa, 9 September: 9.9 µg/m³Nampa, 10 September: 10.6 µg/m³Nampa, 11 September: 5.5 µg/m³Nampa, 12 September: 5.3 µg/m³Nampa, 13 September: 9.8 µg/m³MeridianMeridian, 29 August: 10.8 µg/m³Meridian, 30 August: 10.9 µg/m³Meridian, 31 August: 9.8 µg/m³Meridian, 1 September: 12.4 µg/m³Meridian, 2 September: 9.3 µg/m³Meridian, 3 September: 10.6 µg/m³Meridian, 4 September: 17.0 µg/m³Meridian, 5 September: 30.1 µg/m³, 4.9× its usual 6.2Meridian, 6 September: 17.8 µg/m³Meridian, 7 September: 10.4 µg/m³Meridian, 8 September: 6.0 µg/m³Meridian, 9 September: 6.3 µg/m³Meridian, 10 September: no readingMeridian, 11 September: no readingMeridian, 12 September: no readingMeridian, 13 September: no readingBoiseBoise, 29 August: 10.3 µg/m³Boise, 30 August: 10.9 µg/m³Boise, 31 August: 9.5 µg/m³Boise, 1 September: 10.6 µg/m³Boise, 2 September: 10.5 µg/m³Boise, 3 September: 9.6 µg/m³Boise, 4 September: 14.5 µg/m³Boise, 5 September: 29.8 µg/m³, 5.5× its usual 5.4Boise, 6 September: 19.0 µg/m³Boise, 7 September: 10.4 µg/m³Boise, 8 September: 6.5 µg/m³Boise, 9 September: 6.1 µg/m³Boise, 10 September: 9.6 µg/m³Boise, 11 September: 4.8 µg/m³Boise, 12 September: 4.9 µg/m³Boise, 13 September: 6.2 µg/m³RexburgRexburg, 29 August: 9.5 µg/m³Rexburg, 30 August: 9.0 µg/m³Rexburg, 31 August: 9.2 µg/m³Rexburg, 1 September: 10.5 µg/m³Rexburg, 2 September: 8.3 µg/m³Rexburg, 3 September: 10.2 µg/m³Rexburg, 4 September: 14.6 µg/m³Rexburg, 5 September: 29.7 µg/m³, 4.2× its usual 7.0Rexburg, 6 September: 21.7 µg/m³Rexburg, 7 September: 9.7 µg/m³Rexburg, 8 September: 6.3 µg/m³Rexburg, 9 September: 7.7 µg/m³Rexburg, 10 September: 5.8 µg/m³Rexburg, 11 September: 6.4 µg/m³Rexburg, 12 September: 5.8 µg/m³Rexburg, 13 September: 5.8 µg/m³Idaho FallsIdaho Falls, 29 August: 11.9 µg/m³Idaho Falls, 30 August: 9.8 µg/m³Idaho Falls, 31 August: 11.3 µg/m³Idaho Falls, 1 September: 10.7 µg/m³Idaho Falls, 2 September: 9.1 µg/m³Idaho Falls, 3 September: 11.4 µg/m³Idaho Falls, 4 September: 12.4 µg/m³Idaho Falls, 5 September: 29.3 µg/m³, 5.9× its usual 4.5Idaho Falls, 6 September: 24.7 µg/m³Idaho Falls, 7 September: 6.7 µg/m³Idaho Falls, 8 September: 5.9 µg/m³Idaho Falls, 9 September: 5.9 µg/m³Idaho Falls, 10 September: 3.3 µg/m³Idaho Falls, 11 September: 4.4 µg/m³Idaho Falls, 12 September: 4.2 µg/m³Idaho Falls, 13 September: 3.5 µg/m³Walla WallaWalla Walla, 29 August: 12.9 µg/m³Walla Walla, 30 August: 12.5 µg/m³Walla Walla, 31 August: 11.7 µg/m³Walla Walla, 1 September: 12.4 µg/m³Walla Walla, 2 September: 13.0 µg/m³Walla Walla, 3 September: 14.0 µg/m³Walla Walla, 4 September: 15.7 µg/m³Walla Walla, 5 September: 27.1 µg/m³, 4.6× its usual 5.9Walla 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/m³ButteButte, 29 August: 8.5 µg/m³Butte, 30 August: 9.9 µg/m³Butte, 31 August: 13.2 µg/m³Butte, 1 September: 10.8 µg/m³Butte, 2 September: 11.2 µg/m³Butte, 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/m³29 Aug311 Sep24681012
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
SquamishBritish Columbia, Canada4 173.03 September7.025×
West VancouverBritish Columbia, Canada3 87.23 September5.217×
WenatcheeWashington, United States3 83.36 September5.216×
Sherwood ParkAlberta, Canada8 126.01 September8.016×
St. AlbertAlberta, Canada7 126.01 September8.215×
EdmontonAlberta, Canada8 140.01 September11.412×
CalgaryAlberta, Canada9 100.32 September10.19.9×
LethbridgeAlberta, Canada6 72.82 September7.99.2×
YakimaWashington, United States3 58.04 September6.49.1×
CranbrookBritish Columbia, Canada5 56.27 September6.48.8×
Tri-CitiesWashington, United States2 40.26 September4.78.0×
EllensburgWashington, United States2 41.36 September5.27.9×
KirklandWashington, United States2 38.85 September3.57.8×
Inglewood-Finn HillWashington, United States2 37.55 September4.17.5×
CoquitlamBritish Columbia, Canada1 40.13 September5.47.4×
BurnabyBritish Columbia, Canada1 37.53 September5.46.9×
North VancouverBritish Columbia, Canada1 35.13 September5.16.9×
Medicine HatAlberta, Canada3 48.02 September7.26.7×
SpokaneWashington, United States4 43.56 September6.66.6×
Spokane ValleyWashington, United States4 39.06 September5.96.6×
Swift CurrentSaskatchewan, Canada2 53.42 September8.26.5×
Strawberry HillBritish Columbia, Canada1 34.83 September5.46.4×
VancouverBritish Columbia, Canada1 34.53 September5.46.4×
MissoulaMontana, United States3 33.46 September5.36.3×
MissionBritish Columbia, Canada3 32.33 September5.16.3×
Red DeerAlberta, Canada7 58.62 September9.46.2×
ButteMontana, United States2 31.96 September5.26.1×
Port CoquitlamBritish Columbia, Canada1 31.03 September5.16.1×
ShorelineWashington, United States1 33.75 September5.66.0×
Idaho FallsIdaho, United States1 29.35 September4.55.9×
SunnysideWashington, United States2 39.86 September6.95.8×
PullmanWashington, United States2 34.25 September6.15.6×
BoiseIdaho, United States1 29.85 September5.45.5×
KelownaBritish Columbia, Canada3 42.75 September7.95.4×
Coeur d'AleneIdaho, United States3 37.75 September7.05.4×
AirdrieAlberta, Canada1 41.94 September7.95.3×
HermistonOregon, United States2 31.45 September6.05.2×
VernonBritish Columbia, Canada4 42.45 September8.35.1×
AbbotsfordBritish Columbia, Canada1 29.73 September6.05.0×
MeridianIdaho, United States1 30.15 September6.24.9×
MoscowIdaho, United States2 34.55 September7.34.7×
ChilliwackBritish Columbia, Canada3 31.33 September6.64.7×
BillingsMontana, United States2 31.13 September6.74.6×
Walla WallaWashington, United States2 27.15 September5.94.6×
BozemanMontana, United States1 26.24 September5.84.5×
NampaIdaho, United States1 30.55 September7.14.3×
RexburgIdaho, United States1 29.75 September7.04.2×
LewistonIdaho, United States2 35.15 September8.64.1×
Moses LakeWashington, United States2 26.54 September6.74.0×
KamloopsBritish Columbia, Canada4 33.97 September8.83.9×
HelenaMontana, United States3 29.87 September7.73.9×
ReginaSaskatchewan, Canada1 33.92 September10.23.3×
Great FallsMontana, United States3 33.03 September11.62.8×
SaskatoonSaskatchewan, Canada1 26.02 September10.52.5×

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

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

Use this page

SmogRank, North-western United States and Canada, 1 to 10 September 2025: 54 cities with PM2.5 at twice their usual or more, 1 to 10 September 2025, smogrank.com/episodes/2025-09-01-north-western-united-states-and-canada (accessed 4 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.