SmogRank / Episodes / United States
North-western United States and Canada, 10 to 16 August 2026
For 7 days, from 10 to 16 August 2026, 31 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Vernon, British Columbia, Canada: 142.0 µg/m³ on 10 August, about 16× its usual 9.1.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 31 in 2 countries
Days 7 10 to 16 August 2026
Worst day 10 August 14 cities counted
Furthest above usual 20× Wenatchee
Day by day
Play 10 August 14 cities at twice their usual or more
Coeur d'Alene Moscow Pullman Calgary Airdrie Medicine Hat Boise Meridian Idaho Falls Hermiston Pocatello Swift Current Monroe Union Hill-Novelty Hill Redmond North Creek Marysville Bellevue Bothell Kirkland Renton Inglewood-Finn Hill Auburn Kent Columbia City Picnic Point-North Lynnwood Abbotsford Seattle Shoreline Mount Vernon Burien Parkland Tacoma Bellingham Anacortes Bremerton Langley Gresham Lacey Port Coquitlam Coquitlam Salmon Creek Vancouver Strawberry Hill Oregon City Milwaukie Portland Centralia Burnaby Canby Longview Tigard Delta Beaverton North Vancouver Vancouver Richmond West Vancouver Woodburn Saskatoon Hillsboro Squamish Forest Grove Salem Albany Eugene Casper Redmond Red Deer Bend Nampa Lewiston Great Falls Helena Lethbridge Kennewick Spokane Valley Pendleton Spokane Butte Walla Walla Sunnyside Sheridan Billings Tri-Cities Pasco The Dalles Moses Lake Chilliwack Missoula Bozeman Cranbrook Yakima Kamloops Ellensburg Kelowna Vernon Wenatchee 7 Aug 8 9 10 11 12 13 14 15 16 17 18 19 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
Vernon Vernon, 7 August: 102.0 µg/m³ Vernon, 8 August: 71.8 µg/m³ Vernon, 9 August: 102.0 µg/m³ Vernon, 10 August: 142.0 µg/m³, 16× its usual 9.1 Vernon, 11 August: 118.0 µg/m³, 13× its usual 9.2 Vernon, 12 August: 7.5 µg/m³ Vernon, 13 August: 9.3 µg/m³ Vernon, 14 August: 8.7 µg/m³ Vernon, 15 August: 22.6 µg/m³ Vernon, 16 August: 39.3 µg/m³, 4.2× its usual 9.3 Vernon, 17 August: 23.4 µg/m³ Vernon, 18 August: 17.9 µg/m³ Vernon, 19 August: 20.2 µg/m³ Kamloops Kamloops, 7 August: 191.0 µg/m³ Kamloops, 8 August: 140.0 µg/m³ Kamloops, 9 August: 167.0 µg/m³ Kamloops, 10 August: 97.5 µg/m³, 8.7× its usual 11.2 Kamloops, 11 August: 18.4 µg/m³ Kamloops, 12 August: 8.0 µg/m³ Kamloops, 13 August: 9.3 µg/m³ Kamloops, 14 August: 19.3 µg/m³ Kamloops, 15 August: 43.0 µg/m³ Kamloops, 16 August: 23.6 µg/m³ Kamloops, 17 August: 27.5 µg/m³ Kamloops, 18 August: 33.2 µg/m³ Kamloops, 19 August: 29.6 µg/m³ Cranbrook Cranbrook, 7 August: 84.2 µg/m³ Cranbrook, 8 August: 63.8 µg/m³ Cranbrook, 9 August: 93.4 µg/m³ Cranbrook, 10 August: 68.4 µg/m³, 7.7× its usual 8.9 Cranbrook, 11 August: 58.5 µg/m³, 7.0× its usual 8.4 Cranbrook, 12 August: 29.2 µg/m³, 3.4× its usual 8.5 Cranbrook, 13 August: 8.2 µg/m³ Cranbrook, 14 August: 2.3 µg/m³ Cranbrook, 15 August: 8.7 µg/m³ Cranbrook, 16 August: 15.5 µg/m³ Cranbrook, 17 August: 18.1 µg/m³ Cranbrook, 18 August: 34.5 µg/m³ Cranbrook, 19 August: 38.5 µg/m³ Bozeman Bozeman, 7 August: 44.8 µg/m³ Bozeman, 8 August: 65.0 µg/m³ Bozeman, 9 August: 45.7 µg/m³ Bozeman, 10 August: 61.0 µg/m³, 7.6× its usual 8.0 Bozeman, 11 August: 42.8 µg/m³, 5.4× its usual 7.9 Bozeman, 12 August: 26.0 µg/m³, 3.3× its usual 8.0 Bozeman, 13 August: 13.1 µg/m³ Bozeman, 14 August: 5.3 µg/m³ Bozeman, 15 August: 5.3 µg/m³ Bozeman, 16 August: 5.9 µg/m³ Bozeman, 17 August: 4.8 µg/m³ Bozeman, 18 August: 5.7 µg/m³ Bozeman, 19 August: 9.7 µg/m³ Missoula Missoula, 7 August: 37.6 µg/m³ Missoula, 8 August: 26.9 µg/m³ Missoula, 9 August: 46.7 µg/m³ Missoula, 10 August: 55.1 µg/m³, 7.5× its usual 7.3 Missoula, 11 August: 47.1 µg/m³, 6.3× its usual 7.5 Missoula, 12 August: 30.5 µg/m³, 4.1× its usual 7.5 Missoula, 13 August: 7.8 µg/m³ Missoula, 14 August: 8.9 µg/m³ Missoula, 15 August: 8.8 µg/m³ Missoula, 16 August: 3.0 µg/m³ Missoula, 17 August: 3.6 µg/m³ Missoula, 18 August: 8.8 µg/m³ Missoula, 19 August: 14.2 µg/m³ Great Falls Great Falls, 7 August: 23.6 µg/m³ Great Falls, 8 August: 40.5 µg/m³ Great Falls, 9 August: 37.3 µg/m³ Great Falls, 10 August: 44.5 µg/m³, 3.3× its usual 13.3 Great Falls, 11 August: 33.4 µg/m³, 2.5× its usual 13.2 Great Falls, 12 August: 20.9 µg/m³ Great Falls, 13 August: 12.8 µg/m³ Great Falls, 14 August: 9.5 µg/m³ Great Falls, 15 August: 8.2 µg/m³ Great Falls, 16 August: 11.0 µg/m³ Great Falls, 17 August: 12.9 µg/m³ Great Falls, 18 August: 15.8 µg/m³ Great Falls, 19 August: 21.9 µg/m³ Spokane Spokane, 7 August: 49.3 µg/m³ Spokane, 8 August: 50.0 µg/m³ Spokane, 9 August: 75.2 µg/m³ Spokane, 10 August: 36.5 µg/m³, 4.0× its usual 9.2 Spokane, 11 August: 24.4 µg/m³ Spokane, 12 August: 28.4 µg/m³, 3.1× its usual 9.2 Spokane, 13 August: 18.5 µg/m³ Spokane, 14 August: 8.4 µg/m³ Spokane, 15 August: 11.9 µg/m³ Spokane, 16 August: 13.0 µg/m³ Spokane, 17 August: 13.9 µg/m³ Spokane, 18 August: 17.4 µg/m³ Spokane, 19 August: 15.3 µg/m³ Moses Lake Moses Lake, 7 August: 40.4 µg/m³ Moses Lake, 8 August: 44.9 µg/m³ Moses Lake, 9 August: 87.1 µg/m³ Moses Lake, 10 August: 36.3 µg/m³, 4.8× its usual 7.5 Moses Lake, 11 August: 42.0 µg/m³, 5.6× its usual 7.5 Moses Lake, 12 August: 36.4 µg/m³, 4.9× its usual 7.5 Moses Lake, 13 August: 16.5 µg/m³ Moses Lake, 14 August: 10.7 µg/m³ Moses Lake, 15 August: 18.8 µg/m³ Moses Lake, 16 August: 21.0 µg/m³ Moses Lake, 17 August: 21.9 µg/m³ Moses Lake, 18 August: 17.7 µg/m³ Moses Lake, 19 August: 15.2 µg/m³ Spokane Valley Spokane Valley, 7 August: 46.5 µg/m³ Spokane Valley, 8 August: 59.8 µg/m³ Spokane Valley, 9 August: 82.8 µg/m³ Spokane Valley, 10 August: 33.8 µg/m³, 3.8× its usual 9.0 Spokane Valley, 11 August: 27.9 µg/m³, 3.1× its usual 9.0 Spokane Valley, 12 August: 29.9 µg/m³, 3.4× its usual 8.9 Spokane Valley, 13 August: 17.8 µg/m³ Spokane Valley, 14 August: 8.4 µg/m³ Spokane Valley, 15 August: 12.1 µg/m³ Spokane Valley, 16 August: 12.6 µg/m³ Spokane Valley, 17 August: 13.7 µg/m³ Spokane Valley, 18 August: 17.8 µg/m³ Spokane Valley, 19 August: 16.5 µg/m³ Butte Butte, 7 August: 59.8 µg/m³ Butte, 8 August: 57.6 µg/m³ Butte, 9 August: 36.1 µg/m³ Butte, 10 August: 33.3 µg/m³, 4.2× its usual 7.9 Butte, 11 August: 32.3 µg/m³, 4.0× its usual 8.1 Butte, 12 August: 25.5 µg/m³, 3.2× its usual 8.0 Butte, 13 August: 12.1 µg/m³ Butte, 14 August: 4.8 µg/m³ Butte, 15 August: 4.3 µg/m³ Butte, 16 August: 3.6 µg/m³ Butte, 17 August: 3.5 µg/m³ Butte, 18 August: 6.2 µg/m³ Butte, 19 August: 11.6 µg/m³ Helena Helena, 7 August: 35.3 µg/m³ Helena, 8 August: 30.3 µg/m³ Helena, 9 August: 29.0 µg/m³ Helena, 10 August: 32.9 µg/m³, 3.5× its usual 9.4 Helena, 11 August: 32.2 µg/m³, 3.4× its usual 9.4 Helena, 12 August: 20.7 µg/m³ Helena, 13 August: 4.1 µg/m³ Helena, 14 August: 3.0 µg/m³ Helena, 15 August: 5.1 µg/m³ Helena, 16 August: 5.7 µg/m³ Helena, 17 August: 5.5 µg/m³ Helena, 18 August: 6.4 µg/m³ Helena, 19 August: 14.0 µg/m³ Billings Billings, 7 August: 24.8 µg/m³ Billings, 8 August: 41.4 µg/m³ Billings, 9 August: 40.6 µg/m³ Billings, 10 August: 32.3 µg/m³, 4.4× its usual 7.3 Billings, 11 August: 26.1 µg/m³, 3.6× its usual 7.3 Billings, 12 August: 20.6 µg/m³ Billings, 13 August: 10.1 µg/m³ Billings, 14 August: 3.6 µg/m³ Billings, 15 August: 8.1 µg/m³ Billings, 16 August: 7.5 µg/m³ Billings, 17 August: 5.7 µg/m³ Billings, 18 August: 7.0 µg/m³ Billings, 19 August: 9.1 µg/m³ Sheridan Sheridan, 7 August: 29.1 µg/m³ Sheridan, 8 August: 36.8 µg/m³ Sheridan, 9 August: 34.8 µg/m³ Sheridan, 10 August: 30.1 µg/m³, 4.4× its usual 6.8 Sheridan, 11 August: 22.0 µg/m³ Sheridan, 12 August: 20.2 µg/m³ Sheridan, 13 August: 15.0 µg/m³ Sheridan, 14 August: 9.0 µg/m³ Sheridan, 15 August: 8.4 µg/m³ Sheridan, 16 August: 5.9 µg/m³ Sheridan, 17 August: 4.4 µg/m³ Sheridan, 18 August: 4.0 µg/m³ Sheridan, 19 August: 8.6 µg/m³ Red Deer Red Deer, 7 August: 8.9 µg/m³ Red Deer, 8 August: 15.3 µg/m³ Red Deer, 9 August: 21.2 µg/m³ Red Deer, 10 August: 28.7 µg/m³, 2.3× its usual 12.3 Red Deer, 11 August: 15.2 µg/m³ Red Deer, 12 August: 7.4 µg/m³ Red Deer, 13 August: 6.5 µg/m³ Red Deer, 14 August: 5.3 µg/m³ Red Deer, 15 August: 7.4 µg/m³ Red Deer, 16 August: 10.2 µg/m³ Red Deer, 17 August: no reading Red Deer, 18 August: 11.0 µg/m³ Red Deer, 19 August: 9.0 µg/m³ Kelowna Kelowna, 7 August: 59.8 µg/m³ Kelowna, 8 August: 20.2 µg/m³ Kelowna, 9 August: 40.8 µg/m³ Kelowna, 10 August: no reading Kelowna, 11 August: 94.3 µg/m³, 11× its usual 8.4 Kelowna, 12 August: 15.3 µg/m³ Kelowna, 13 August: 16.3 µg/m³ Kelowna, 14 August: 8.4 µg/m³ Kelowna, 15 August: 17.2 µg/m³ Kelowna, 16 August: 28.5 µg/m³, 3.3× its usual 8.6 Kelowna, 17 August: 18.6 µg/m³ Kelowna, 18 August: 18.1 µg/m³ Kelowna, 19 August: 18.0 µg/m³ Lethbridge Lethbridge, 7 August: 19.2 µg/m³ Lethbridge, 8 August: 21.3 µg/m³ Lethbridge, 9 August: 19.6 µg/m³ Lethbridge, 10 August: 22.1 µg/m³ Lethbridge, 11 August: 33.4 µg/m³, 3.6× its usual 9.3 Lethbridge, 12 August: 10.6 µg/m³ Lethbridge, 13 August: 7.7 µg/m³ Lethbridge, 14 August: 6.8 µg/m³ Lethbridge, 15 August: 7.0 µg/m³ Lethbridge, 16 August: 11.9 µg/m³ Lethbridge, 17 August: 15.4 µg/m³ Lethbridge, 18 August: 38.7 µg/m³ Lethbridge, 19 August: 27.5 µg/m³ Wenatchee Wenatchee, 7 August: 99.9 µg/m³ Wenatchee, 8 August: 8.6 µg/m³ Wenatchee, 9 August: 14.0 µg/m³ Wenatchee, 10 August: 5.2 µg/m³ Wenatchee, 11 August: 6.1 µg/m³ Wenatchee, 12 August: 38.7 µg/m³, 7.7× its usual 5.0 Wenatchee, 13 August: 57.5 µg/m³, 12× its usual 5.0 Wenatchee, 14 August: 35.2 µg/m³, 7.0× its usual 5.0 Wenatchee, 15 August: 97.8 µg/m³, 20× its usual 5.0 Wenatchee, 16 August: 76.5 µg/m³, 15× its usual 5.1 Wenatchee, 17 August: 45.9 µg/m³ Wenatchee, 18 August: 17.1 µg/m³ Wenatchee, 19 August: 16.9 µg/m³ Yakima Yakima, 7 August: 24.6 µg/m³ Yakima, 8 August: 10.4 µg/m³ Yakima, 9 August: 36.2 µg/m³ Yakima, 10 August: 2.8 µg/m³ Yakima, 11 August: 6.3 µg/m³ Yakima, 12 August: 25.9 µg/m³, 4.0× its usual 6.4 Yakima, 13 August: 48.5 µg/m³, 7.8× its usual 6.2 Yakima, 14 August: 27.1 µg/m³, 4.4× its usual 6.2 Yakima, 15 August: 28.4 µg/m³, 4.6× its usual 6.2 Yakima, 16 August: 22.0 µg/m³ Yakima, 17 August: 15.3 µg/m³ Yakima, 18 August: 18.2 µg/m³ Yakima, 19 August: 14.2 µg/m³ Ellensburg Ellensburg, 7 August: 24.7 µg/m³ Ellensburg, 8 August: 12.4 µg/m³ Ellensburg, 9 August: 19.5 µg/m³ Ellensburg, 10 August: 8.5 µg/m³ Ellensburg, 11 August: 8.5 µg/m³ Ellensburg, 12 August: 17.9 µg/m³ Ellensburg, 13 August: 60.6 µg/m³, 11× its usual 5.6 Ellensburg, 14 August: 46.2 µg/m³, 8.4× its usual 5.5 Ellensburg, 15 August: 33.3 µg/m³, 5.9× its usual 5.6 Ellensburg, 16 August: 18.9 µg/m³ Ellensburg, 17 August: 14.6 µg/m³ Ellensburg, 18 August: 17.8 µg/m³ Ellensburg, 19 August: 13.5 µg/m³ Sunnyside Sunnyside, 7 August: 26.8 µg/m³ Sunnyside, 8 August: 10.8 µg/m³ Sunnyside, 9 August: 10.6 µg/m³ Sunnyside, 10 August: 7.6 µg/m³ Sunnyside, 11 August: 6.9 µg/m³ Sunnyside, 12 August: 21.2 µg/m³ Sunnyside, 13 August: 33.9 µg/m³, 4.3× its usual 7.8 Sunnyside, 14 August: 21.8 µg/m³ Sunnyside, 15 August: 20.8 µg/m³ Sunnyside, 16 August: 20.0 µg/m³ Sunnyside, 17 August: 16.3 µg/m³ Sunnyside, 18 August: 14.7 µg/m³ Sunnyside, 19 August: 12.8 µg/m³ Lewiston Lewiston, 7 August: 51.9 µg/m³ Lewiston, 8 August: 27.0 µg/m³ Lewiston, 9 August: 22.8 µg/m³ Lewiston, 10 August: 19.9 µg/m³ Lewiston, 11 August: 22.2 µg/m³ Lewiston, 12 August: 16.9 µg/m³ Lewiston, 13 August: 29.3 µg/m³, 2.9× its usual 10.1 Lewiston, 14 August: 21.4 µg/m³ Lewiston, 15 August: 21.6 µg/m³ Lewiston, 16 August: 14.5 µg/m³ Lewiston, 17 August: 12.4 µg/m³ Lewiston, 18 August: 13.9 µg/m³ Lewiston, 19 August: 24.3 µg/m³ Tri-Cities Tri-Cities, 7 August: 33.0 µg/m³ Tri-Cities, 8 August: 23.0 µg/m³ Tri-Cities, 9 August: 13.9 µg/m³ Tri-Cities, 10 August: 6.7 µg/m³ Tri-Cities, 11 August: 5.4 µg/m³ Tri-Cities, 12 August: 18.5 µg/m³ Tri-Cities, 13 August: 27.8 µg/m³, 4.9× its usual 5.7 Tri-Cities, 14 August: 11.8 µg/m³ Tri-Cities, 15 August: 17.8 µg/m³ Tri-Cities, 16 August: 22.1 µg/m³ Tri-Cities, 17 August: 15.6 µg/m³ Tri-Cities, 18 August: 13.1 µg/m³ Tri-Cities, 19 August: 14.7 µg/m³ Nampa Nampa, 7 August: 77.5 µg/m³ Nampa, 8 August: 70.8 µg/m³ Nampa, 9 August: 35.7 µg/m³ Nampa, 10 August: 34.3 µg/m³ Nampa, 11 August: 39.4 µg/m³ Nampa, 12 August: 24.3 µg/m³ Nampa, 13 August: 26.3 µg/m³, 2.6× its usual 10.0 Nampa, 14 August: 14.1 µg/m³ Nampa, 15 August: 8.4 µg/m³ Nampa, 16 August: 3.5 µg/m³ Nampa, 17 August: 8.7 µg/m³ Nampa, 18 August: 13.6 µg/m³ Nampa, 19 August: 16.4 µg/m³ Pasco Pasco, 7 August: 32.3 µg/m³ Pasco, 8 August: 19.0 µg/m³ Pasco, 9 August: 11.8 µg/m³ Pasco, 10 August: 6.1 µg/m³ Pasco, 11 August: 5.7 µg/m³ Pasco, 12 August: 17.4 µg/m³ Pasco, 13 August: 26.1 µg/m³, 5.2× its usual 4.4 Pasco, 14 August: 13.2 µg/m³ Pasco, 15 August: 19.6 µg/m³ Pasco, 16 August: 27.1 µg/m³, 5.4× its usual 4.0 Pasco, 17 August: 18.1 µg/m³ Pasco, 18 August: 13.3 µg/m³ Pasco, 19 August: 15.5 µg/m³ Redmond Redmond, 7 August: 21.4 µg/m³ Redmond, 8 August: 14.2 µg/m³ Redmond, 9 August: 13.3 µg/m³ Redmond, 10 August: 34.2 µg/m³ Redmond, 11 August: 34.7 µg/m³ Redmond, 12 August: 16.7 µg/m³ Redmond, 13 August: 25.9 µg/m³, 2.1× its usual 12.3 Redmond, 14 August: 25.0 µg/m³, 2.1× its usual 12.1 Redmond, 15 August: 23.2 µg/m³ Redmond, 16 August: 20.0 µg/m³ Redmond, 17 August: 39.2 µg/m³ Redmond, 18 August: 30.7 µg/m³ Redmond, 19 August: 29.4 µg/m³ Bend Bend, 7 August: 18.0 µg/m³ Bend, 8 August: 12.3 µg/m³ Bend, 9 August: 4.7 µg/m³ Bend, 10 August: 23.7 µg/m³ Bend, 11 August: 23.3 µg/m³ Bend, 12 August: 6.5 µg/m³ Bend, 13 August: 25.4 µg/m³, 2.6× its usual 9.9 Bend, 14 August: 18.3 µg/m³ Bend, 15 August: 17.6 µg/m³ Bend, 16 August: 11.1 µg/m³ Bend, 17 August: 15.1 µg/m³ Bend, 18 August: 7.6 µg/m³ Bend, 19 August: 12.0 µg/m³ Chilliwack Chilliwack, 7 August: 19.9 µg/m³ Chilliwack, 8 August: 9.5 µg/m³ Chilliwack, 9 August: 5.7 µg/m³ Chilliwack, 10 August: 6.0 µg/m³ Chilliwack, 11 August: 4.7 µg/m³ Chilliwack, 12 August: 6.5 µg/m³ Chilliwack, 13 August: 21.9 µg/m³ Chilliwack, 14 August: 33.5 µg/m³, 5.9× its usual 5.7 Chilliwack, 15 August: 15.2 µg/m³ Chilliwack, 16 August: 6.7 µg/m³ Chilliwack, 17 August: 12.3 µg/m³ Chilliwack, 18 August: 13.8 µg/m³ Chilliwack, 19 August: 9.8 µg/m³ The Dalles The Dalles, 7 August: 19.3 µg/m³ The Dalles, 8 August: 11.2 µg/m³ The Dalles, 9 August: 5.0 µg/m³ The Dalles, 10 August: 5.3 µg/m³ The Dalles, 11 August: 5.8 µg/m³ The Dalles, 12 August: 5.1 µg/m³ The Dalles, 13 August: 22.8 µg/m³ The Dalles, 14 August: 28.6 µg/m³, 5.4× its usual 5.3 The Dalles, 15 August: 18.7 µg/m³ The Dalles, 16 August: 10.8 µg/m³ The Dalles, 17 August: 12.2 µg/m³ The Dalles, 18 August: 14.7 µg/m³ The Dalles, 19 August: 23.6 µg/m³ Pendleton Pendleton, 7 August: 48.1 µg/m³ Pendleton, 8 August: 31.4 µg/m³ Pendleton, 9 August: 14.6 µg/m³ Pendleton, 10 August: 14.8 µg/m³ Pendleton, 11 August: 15.8 µg/m³ Pendleton, 12 August: 12.2 µg/m³ Pendleton, 13 August: 20.9 µg/m³ Pendleton, 14 August: 21.4 µg/m³ Pendleton, 15 August: 29.7 µg/m³, 3.9× its usual 7.7 Pendleton, 16 August: 26.9 µg/m³, 3.5× its usual 7.7 Pendleton, 17 August: 26.2 µg/m³ Pendleton, 18 August: 15.1 µg/m³ Pendleton, 19 August: 17.2 µg/m³ Walla Walla Walla Walla, 7 August: 51.0 µg/m³ Walla Walla, 8 August: 18.4 µg/m³ Walla Walla, 9 August: 8.0 µg/m³ Walla Walla, 10 August: 10.3 µg/m³ Walla Walla, 11 August: 11.0 µg/m³ Walla Walla, 12 August: 14.0 µg/m³ Walla Walla, 13 August: 24.3 µg/m³ Walla Walla, 14 August: 20.0 µg/m³ Walla Walla, 15 August: 21.4 µg/m³ Walla Walla, 16 August: 31.1 µg/m³, 4.3× its usual 7.2 Walla Walla, 17 August: 18.2 µg/m³ Walla Walla, 18 August: 16.7 µg/m³ Walla Walla, 19 August: 19.6 µg/m³ Kennewick Kennewick, 7 August: 32.0 µg/m³ Kennewick, 8 August: 20.0 µg/m³ Kennewick, 9 August: 14.0 µg/m³ Kennewick, 10 August: 6.5 µg/m³ Kennewick, 11 August: 6.1 µg/m³ Kennewick, 12 August: 14.6 µg/m³ Kennewick, 13 August: 26.4 µg/m³ Kennewick, 14 August: 12.9 µg/m³ Kennewick, 15 August: 17.5 µg/m³ Kennewick, 16 August: 25.2 µg/m³, 3.8× its usual 6.7 Kennewick, 17 August: 20.1 µg/m³ Kennewick, 18 August: 13.7 µg/m³ Kennewick, 19 August: 15.2 µg/m³ 7 Aug 9 11 13 15 17 19 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. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Wenatchee Washington, United States 5 15 August 5.0 20× Vernon British Columbia, Canada 3 10 August 9.1 16× Kelowna British Columbia, Canada 2 11 August 8.4 11× Ellensburg Washington, United States 3 13 August 5.6 11× Kamloops British Columbia, Canada 1 10 August 11.2 8.7× Yakima Washington, United States 4 13 August 6.2 7.8× Cranbrook British Columbia, Canada 3 10 August 8.9 7.7× Bozeman Montana, United States 3 10 August 8.0 7.6× Missoula Montana, United States 3 10 August 7.3 7.5× Chilliwack British Columbia, Canada 1 14 August 5.7 5.9× Moses Lake Washington, United States 3 11 August 7.5 5.6× The Dalles Oregon, United States 1 14 August 5.3 5.4× Pasco Washington, United States 2 16 August 4.0 5.4× Tri-Cities Washington, United States 1 13 August 5.7 4.9× Billings Montana, United States 2 10 August 7.3 4.4× Sheridan Wyoming, United States 1 10 August 6.8 4.4× Sunnyside Washington, United States 1 13 August 7.8 4.3× Walla Walla Washington, United States 1 16 August 7.2 4.3× Butte Montana, United States 3 10 August 7.9 4.2× Spokane Washington, United States 2 10 August 9.2 4.0× Pendleton Oregon, United States 2 15 August 7.7 3.9× Spokane Valley Washington, United States 3 10 August 9.0 3.8× Kennewick Washington, United States 1 16 August 6.7 3.8× Lethbridge Alberta, Canada 1 11 August 9.3 3.6× Helena Montana, United States 2 10 August 9.4 3.5× Great Falls Montana, United States 2 10 August 13.3 3.3× Lewiston Idaho, United States 1 13 August 10.1 2.9× Nampa Idaho, United States 1 13 August 10.0 2.6× Bend Oregon, United States 1 13 August 9.9 2.6× Red Deer Alberta, Canada 1 10 August 12.3 2.3× Redmond Oregon, United States 2 13 August 12.3 2.1×
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 32 of 141 episodes in the United States and Canada since our records began, by cities reached.
Eastern United States and Canada, 25 June to 2 July 2023 280 North-eastern United States and Canada, July 2026 264 Eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, 30 July to 9 August 2025 241 Eastern United States and Canada, July 2023 240 North-eastern United States and Canada, 3 to 9 June 2025 196 Eastern United States and Canada, 14 to 19 June 2023 161 North-eastern United States and Canada, 12 to 16 July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, 10 to 14 June 2025 104 North-western United States and Canada, 4 to 11 August 2026 99 North-eastern United States and Canada, 14 to 19 February 2026 96 North-western United States and Canada, 10 to 16 August 2026 31 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, 10 to 16 August 2026: 31 cities with PM2.5 at twice their usual or more, 10 to 16 August 2026, smogrank.com/episodes/2026-08-10-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.
