SmogRank / Episodes / United States
North-western United States and Canada, July 2024
For 5 days, from 20 to 24 July 2024, 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 Prince Albert, Saskatchewan, Canada: 203.0 µg/m³ on 21 July, about 14× its usual 14.7.
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 5 20 to 24 July 2024
Worst day 22 July 22 cities counted
Furthest above usual 16× Sherwood Park
Day by day
Play 22 July 22 cities at twice their usual or more
Bozeman Rexburg Idaho Falls Pocatello Conda Twin Falls North Ogden Boise Coeur d'Alene Moscow Meridian Rock Springs Bountiful Pullman Salt Lake City Nampa Magna West Valley City Millcreek West Jordan Spokane Valley Herriman Tooele Highland Spokane Orem Spanish Fork Walla Walla Pendleton Tri-Cities Hermiston Moses Lake Grand Junction Laramie Sunnyside Penticton Vernon Kelowna Wenatchee Cedar City Yakima Ellensburg Boulder Denver The Dalles Littleton Redmond Bend Spanish Springs Reno Carson City Pueblo Truckee South Lake Tahoe Paradise Lincoln Folsom Roseville Yuba City Florin Sacramento Elk Grove Galt Modesto Stockton Manteca Tracy Lewiston Calgary Greeley Cranbrook Sheridan Butte Lethbridge Billings Great Falls Thornton Colorado Springs Red Deer Fort Collins Airdrie Helena Longmont Ken Caryl Casper Kamloops Rapid City Gillette Cheyenne Medicine Hat Swift Current Missoula Regina Saskatoon Edmonton St. Albert Prince Albert Sherwood Park 17 Jul 18 19 20 21 22 23 24 25 26 27 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
Edmonton Edmonton, 17 July: 7.8 µg/m³, 0.6× usual Edmonton, 18 July: 12.1 µg/m³, 0.9× usual Edmonton, 19 July: 34.4 µg/m³, 2.5× usual Edmonton, 20 July: 170.0 µg/m³, 12× usual Edmonton, 21 July: 56.7 µg/m³, 4.1× usual Edmonton, 22 July: 66.3 µg/m³, 4.8× usual Edmonton, 23 July: 95.7 µg/m³, 6.9× usual Edmonton, 24 July: 61.3 µg/m³, 4.4× usual Edmonton, 25 July: 46.1 µg/m³, 3.3× usual Edmonton, 26 July: 13.8 µg/m³, 1.0× usual Edmonton, 27 July: 19.3 µg/m³, 1.4× usual St. Albert St. Albert, 17 July: 8.9 µg/m³, 1.0× usual St. Albert, 18 July: 9.1 µg/m³, 1.0× usual St. Albert, 19 July: 29.5 µg/m³, 3.2× usual St. Albert, 20 July: 120.0 µg/m³, 13× usual St. Albert, 21 July: 36.2 µg/m³, 3.9× usual St. Albert, 22 July: 48.3 µg/m³, 5.2× usual St. Albert, 23 July: 66.2 µg/m³, 7.1× usual St. Albert, 24 July: 36.7 µg/m³, 3.9× usual St. Albert, 25 July: 25.6 µg/m³, 2.8× usual St. Albert, 26 July: 12.0 µg/m³, 1.3× usual St. Albert, 27 July: 15.3 µg/m³, 1.6× usual Prince Albert Prince Albert, 17 July: 24.3 µg/m³, 1.7× usual Prince Albert, 18 July: no reading Prince Albert, 19 July: no reading Prince Albert, 20 July: 70.1 µg/m³, 4.8× usual Prince Albert, 21 July: 203.0 µg/m³, 14× usual Prince Albert, 22 July: 76.9 µg/m³, 5.2× usual Prince Albert, 23 July: 34.7 µg/m³, 2.4× usual Prince Albert, 24 July: 50.5 µg/m³, 3.4× usual Prince Albert, 25 July: 42.0 µg/m³, 2.9× usual Prince Albert, 26 July: 18.0 µg/m³, 1.2× usual Prince Albert, 27 July: 17.7 µg/m³, 1.2× usual Sherwood Park Sherwood Park, 17 July: 5.4 µg/m³, 0.5× usual Sherwood Park, 18 July: 6.3 µg/m³, 0.6× usual Sherwood Park, 19 July: 21.4 µg/m³, 2.2× usual Sherwood Park, 20 July: 44.2 µg/m³, 4.5× usual Sherwood Park, 21 July: no reading Sherwood Park, 22 July: 162.0 µg/m³, 16× usual Sherwood Park, 23 July: no reading Sherwood Park, 24 July: 32.7 µg/m³, 3.3× usual Sherwood Park, 25 July: 23.7 µg/m³, 2.4× usual Sherwood Park, 26 July: 9.5 µg/m³, 1.0× usual Sherwood Park, 27 July: 14.0 µg/m³, 1.4× usual Red Deer Red Deer, 17 July: 9.8 µg/m³, 1.0× usual Red Deer, 18 July: 10.9 µg/m³, 1.1× usual Red Deer, 19 July: 9.7 µg/m³, 1.0× usual Red Deer, 20 July: 28.2 µg/m³, 2.8× usual Red Deer, 21 July: 38.8 µg/m³, 3.9× usual Red Deer, 22 July: 42.7 µg/m³, 4.3× usual Red Deer, 23 July: 84.4 µg/m³, 8.4× usual Red Deer, 24 July: 50.2 µg/m³, 5.0× usual Red Deer, 25 July: 22.8 µg/m³, 2.3× usual Red Deer, 26 July: 5.1 µg/m³, 0.5× usual Red Deer, 27 July: 12.9 µg/m³, 1.3× usual Medicine Hat Medicine Hat, 17 July: 6.0 µg/m³, 0.7× usual Medicine Hat, 18 July: 7.8 µg/m³, 0.9× usual Medicine Hat, 19 July: 13.2 µg/m³, 1.5× usual Medicine Hat, 20 July: 25.0 µg/m³, 2.8× usual Medicine Hat, 21 July: 51.6 µg/m³, 5.7× usual Medicine Hat, 22 July: 45.5 µg/m³, 5.1× usual Medicine Hat, 23 July: 49.1 µg/m³, 5.5× usual Medicine Hat, 24 July: 24.9 µg/m³, 2.8× usual Medicine Hat, 25 July: 33.5 µg/m³, 3.7× usual Medicine Hat, 26 July: 12.5 µg/m³, 1.4× usual Medicine Hat, 27 July: 17.6 µg/m³, 2.0× usual Saskatoon Saskatoon, 17 July: 24.6 µg/m³, 1.8× usual Saskatoon, 18 July: 24.0 µg/m³, 1.7× usual Saskatoon, 19 July: 16.6 µg/m³, 1.2× usual Saskatoon, 20 July: 29.3 µg/m³, 2.1× usual Saskatoon, 21 July: 163.0 µg/m³, 12× usual Saskatoon, 22 July: 93.4 µg/m³, 6.8× usual Saskatoon, 23 July: 45.4 µg/m³, 3.3× usual Saskatoon, 24 July: 46.2 µg/m³, 3.3× usual Saskatoon, 25 July: 37.5 µg/m³, 2.7× usual Saskatoon, 26 July: 12.6 µg/m³, 0.9× usual Saskatoon, 27 July: 23.8 µg/m³, 1.7× usual Regina Regina, 17 July: no reading Regina, 18 July: no reading Regina, 19 July: 17.5 µg/m³, 1.4× usual Regina, 20 July: 22.4 µg/m³, 1.8× usual Regina, 21 July: 49.4 µg/m³, 4.0× usual Regina, 22 July: 79.8 µg/m³, 6.5× usual Regina, 23 July: 48.8 µg/m³, 4.0× usual Regina, 24 July: 38.0 µg/m³, 3.1× usual Regina, 25 July: 29.3 µg/m³, 2.4× usual Regina, 26 July: 19.6 µg/m³, 1.6× usual Regina, 27 July: 12.1 µg/m³, 1.0× usual Rapid City Rapid City, 17 July: 7.1 µg/m³, 0.8× usual Rapid City, 18 July: 8.0 µg/m³, 0.9× usual Rapid City, 19 July: 12.2 µg/m³, 1.4× usual Rapid City, 20 July: 13.7 µg/m³, 1.6× usual Rapid City, 21 July: 49.2 µg/m³, 5.6× usual Rapid City, 22 July: 46.8 µg/m³, 5.3× usual Rapid City, 23 July: 33.6 µg/m³, 3.8× usual Rapid City, 24 July: 33.7 µg/m³, 3.8× usual Rapid City, 25 July: 24.2 µg/m³, 2.7× usual Rapid City, 26 July: 23.9 µg/m³, 2.7× usual Rapid City, 27 July: 15.1 µg/m³, 1.7× usual Great Falls Great Falls, 17 July: 13.9 µg/m³, 1.1× usual Great Falls, 18 July: 21.2 µg/m³, 1.7× usual Great Falls, 19 July: 18.0 µg/m³, 1.4× usual Great Falls, 20 July: 20.6 µg/m³, 1.6× usual Great Falls, 21 July: 41.1 µg/m³, 3.2× usual Great Falls, 22 July: 52.8 µg/m³, 4.1× usual Great Falls, 23 July: 25.2 µg/m³, 2.0× usual Great Falls, 24 July: 27.6 µg/m³, 2.2× usual Great Falls, 25 July: 18.0 µg/m³, 1.4× usual Great Falls, 26 July: 15.8 µg/m³, 1.2× usual Great Falls, 27 July: 19.4 µg/m³, 1.5× usual Swift Current Swift Current, 17 July: no reading Swift Current, 18 July: 13.7 µg/m³, 1.4× usual Swift Current, 19 July: no reading Swift Current, 20 July: no reading Swift Current, 21 July: 28.0 µg/m³, 2.8× usual Swift Current, 22 July: 59.7 µg/m³, 6.0× usual Swift Current, 23 July: 56.4 µg/m³, 5.7× usual Swift Current, 24 July: 24.7 µg/m³, 2.5× usual Swift Current, 25 July: 33.4 µg/m³, 3.4× usual Swift Current, 26 July: 15.9 µg/m³, 1.6× usual Swift Current, 27 July: 14.6 µg/m³, 1.5× usual Helena Helena, 17 July: 18.7 µg/m³, 2.0× usual Helena, 18 July: 22.2 µg/m³, 2.4× usual Helena, 19 July: 20.6 µg/m³, 2.2× usual Helena, 20 July: 13.6 µg/m³, 1.5× usual Helena, 21 July: 28.0 µg/m³, 3.0× usual Helena, 22 July: 42.9 µg/m³, 4.6× usual Helena, 23 July: 18.3 µg/m³, 2.0× usual Helena, 24 July: 21.3 µg/m³, 2.3× usual Helena, 25 July: 19.3 µg/m³, 2.1× usual Helena, 26 July: 35.8 µg/m³, 3.8× usual Helena, 27 July: 28.6 µg/m³, 3.1× usual Kamloops Kamloops, 17 July: 15.7 µg/m³, 1.6× usual Kamloops, 18 July: 16.2 µg/m³, 1.6× usual Kamloops, 19 July: 8.1 µg/m³, 0.8× usual Kamloops, 20 July: 15.1 µg/m³, 1.5× usual Kamloops, 21 July: 26.4 µg/m³, 2.6× usual Kamloops, 22 July: 51.8 µg/m³, 5.2× usual Kamloops, 23 July: 3.7 µg/m³, 0.4× usual Kamloops, 24 July: 7.1 µg/m³, 0.7× usual Kamloops, 25 July: 6.3 µg/m³, 0.6× usual Kamloops, 26 July: 9.1 µg/m³, 0.9× usual Kamloops, 27 July: 20.9 µg/m³, 2.1× usual Calgary Calgary, 17 July: 14.6 µg/m³, 1.3× usual Calgary, 18 July: 19.5 µg/m³, 1.8× usual Calgary, 19 July: 23.0 µg/m³, 2.1× usual Calgary, 20 July: 22.6 µg/m³, 2.0× usual Calgary, 21 July: 22.6 µg/m³, 2.0× usual Calgary, 22 July: 39.0 µg/m³, 3.5× usual Calgary, 23 July: 55.5 µg/m³, 5.0× usual Calgary, 24 July: 139.5 µg/m³, 13× usual Calgary, 25 July: 51.4 µg/m³, 4.6× usual Calgary, 26 July: 15.7 µg/m³, 1.4× usual Calgary, 27 July: 14.5 µg/m³, 1.3× usual Airdrie Airdrie, 17 July: 9.4 µg/m³, 1.2× usual Airdrie, 18 July: 17.2 µg/m³, 2.1× usual Airdrie, 19 July: 16.9 µg/m³, 2.1× usual Airdrie, 20 July: 21.2 µg/m³, 2.6× usual Airdrie, 21 July: 13.6 µg/m³, 1.7× usual Airdrie, 22 July: 35.3 µg/m³, 4.4× usual Airdrie, 23 July: 38.6 µg/m³, 4.8× usual Airdrie, 24 July: 42.1 µg/m³, 5.2× usual Airdrie, 25 July: 26.6 µg/m³, 3.3× usual Airdrie, 26 July: 11.1 µg/m³, 1.4× usual Airdrie, 27 July: 13.3 µg/m³, 1.6× usual Missoula Missoula, 17 July: 17.9 µg/m³, 3.1× usual Missoula, 18 July: 18.2 µg/m³, 3.1× usual Missoula, 19 July: 21.3 µg/m³, 3.7× usual Missoula, 20 July: 17.5 µg/m³, 3.0× usual Missoula, 21 July: 19.9 µg/m³, 3.4× usual Missoula, 22 July: 35.2 µg/m³, 6.1× usual Missoula, 23 July: 24.0 µg/m³, 4.1× usual Missoula, 24 July: 25.5 µg/m³, 4.4× usual Missoula, 25 July: 23.2 µg/m³, 4.0× usual Missoula, 26 July: 13.2 µg/m³, 2.3× usual Missoula, 27 July: 17.0 µg/m³, 2.9× usual Lethbridge Lethbridge, 17 July: 10.0 µg/m³, 1.2× usual Lethbridge, 18 July: 9.2 µg/m³, 1.1× usual Lethbridge, 19 July: 11.0 µg/m³, 1.3× usual Lethbridge, 20 July: 10.3 µg/m³, 1.2× usual Lethbridge, 21 July: 16.1 µg/m³, 1.9× usual Lethbridge, 22 July: 32.1 µg/m³, 3.9× usual Lethbridge, 23 July: 21.6 µg/m³, 2.6× usual Lethbridge, 24 July: 17.6 µg/m³, 2.1× usual Lethbridge, 25 July: 27.0 µg/m³, 3.3× usual Lethbridge, 26 July: 10.1 µg/m³, 1.2× usual Lethbridge, 27 July: 19.2 µg/m³, 2.3× usual Gillette Gillette, 17 July: 10.3 µg/m³, 1.6× usual Gillette, 18 July: 10.7 µg/m³, 1.6× usual Gillette, 19 July: 9.7 µg/m³, 1.5× usual Gillette, 20 July: 10.2 µg/m³, 1.5× usual Gillette, 21 July: 19.3 µg/m³, 2.9× usual Gillette, 22 July: 30.8 µg/m³, 4.7× usual Gillette, 23 July: 35.9 µg/m³, 5.4× usual Gillette, 24 July: 28.6 µg/m³, 4.3× usual Gillette, 25 July: no reading Gillette, 26 July: no reading Gillette, 27 July: 15.5 µg/m³, 2.3× usual Billings Billings, 17 July: 14.6 µg/m³, 2.1× usual Billings, 18 July: 14.3 µg/m³, 2.0× usual Billings, 19 July: 15.0 µg/m³, 2.1× usual Billings, 20 July: 15.8 µg/m³, 2.2× usual Billings, 21 July: 15.4 µg/m³, 2.2× usual Billings, 22 July: 28.0 µg/m³, 3.9× usual Billings, 23 July: 26.9 µg/m³, 3.8× usual Billings, 24 July: 22.4 µg/m³, 3.2× usual Billings, 25 July: 12.0 µg/m³, 1.7× usual Billings, 26 July: 14.7 µg/m³, 2.1× usual Billings, 27 July: 22.2 µg/m³, 3.1× usual Butte Butte, 17 July: 20.8 µg/m³, 3.0× usual Butte, 18 July: 16.6 µg/m³, 2.4× usual Butte, 19 July: 18.7 µg/m³, 2.7× usual Butte, 20 July: 14.9 µg/m³, 2.2× usual Butte, 21 July: 21.9 µg/m³, 3.2× usual Butte, 22 July: 26.2 µg/m³, 3.8× usual Butte, 23 July: 15.2 µg/m³, 2.2× usual Butte, 24 July: 12.4 µg/m³, 1.8× usual Butte, 25 July: 12.9 µg/m³, 1.9× usual Butte, 26 July: 37.6 µg/m³, 5.4× usual Butte, 27 July: 37.7 µg/m³, 5.5× usual Longmont Longmont, 17 July: 14.0 µg/m³, 1.9× usual Longmont, 18 July: 10.2 µg/m³, 1.4× usual Longmont, 19 July: 9.6 µg/m³, 1.3× usual Longmont, 20 July: 9.1 µg/m³, 1.3× usual Longmont, 21 July: 14.0 µg/m³, 1.9× usual Longmont, 22 July: 26.0 µg/m³, 3.6× usual Longmont, 23 July: 34.5 µg/m³, 4.8× usual Longmont, 24 July: 27.6 µg/m³, 3.8× usual Longmont, 25 July: 24.2 µg/m³, 3.4× usual Longmont, 26 July: 19.2 µg/m³, 2.7× usual Longmont, 27 July: 7.9 µg/m³, 1.1× usual Thornton Thornton, 17 July: 10.7 µg/m³, 1.4× usual Thornton, 18 July: 9.8 µg/m³, 1.3× usual Thornton, 19 July: 10.7 µg/m³, 1.4× usual Thornton, 20 July: 9.5 µg/m³, 1.3× usual Thornton, 21 July: 9.9 µg/m³, 1.3× usual Thornton, 22 July: 25.3 µg/m³, 3.3× usual Thornton, 23 July: 32.0 µg/m³, 4.2× usual Thornton, 24 July: 31.7 µg/m³, 4.2× usual Thornton, 25 July: 23.4 µg/m³, 3.1× usual Thornton, 26 July: 18.0 µg/m³, 2.4× usual Thornton, 27 July: 7.4 µg/m³, 1.0× usual Cranbrook Cranbrook, 17 July: 10.4 µg/m³, 1.5× usual Cranbrook, 18 July: 10.8 µg/m³, 1.5× usual Cranbrook, 19 July: 16.3 µg/m³, 2.3× usual Cranbrook, 20 July: 21.4 µg/m³, 3.1× usual Cranbrook, 21 July: 18.5 µg/m³, 2.6× usual Cranbrook, 22 July: 25.3 µg/m³, 3.6× usual Cranbrook, 23 July: 18.5 µg/m³, 2.6× usual Cranbrook, 24 July: 11.3 µg/m³, 1.6× usual Cranbrook, 25 July: 15.9 µg/m³, 2.3× usual Cranbrook, 26 July: 15.8 µg/m³, 2.3× usual Cranbrook, 27 July: 27.9 µg/m³, 4.0× usual Lewiston Lewiston, 17 July: 23.9 µg/m³, 2.9× usual Lewiston, 18 July: 20.7 µg/m³, 2.5× usual Lewiston, 19 July: 15.6 µg/m³, 1.9× usual Lewiston, 20 July: 13.3 µg/m³, 1.6× usual Lewiston, 21 July: 18.5 µg/m³, 2.2× usual Lewiston, 22 July: 25.3 µg/m³, 3.0× usual Lewiston, 23 July: 20.6 µg/m³, 2.5× usual Lewiston, 24 July: 29.5 µg/m³, 3.6× usual Lewiston, 25 July: 24.7 µg/m³, 3.0× usual Lewiston, 26 July: 109.9 µg/m³, 13× usual Lewiston, 27 July: 58.0 µg/m³, 7.0× usual Colorado Springs Colorado Springs, 17 July: 8.6 µg/m³, 1.2× usual Colorado Springs, 18 July: 12.0 µg/m³, 1.7× usual Colorado Springs, 19 July: 9.5 µg/m³, 1.4× usual Colorado Springs, 20 July: 7.3 µg/m³, 1.1× usual Colorado Springs, 21 July: 6.5 µg/m³, 0.9× usual Colorado Springs, 22 July: 23.7 µg/m³, 3.4× usual Colorado Springs, 23 July: 29.6 µg/m³, 4.3× usual Colorado Springs, 24 July: 26.7 µg/m³, 3.9× usual Colorado Springs, 25 July: 23.3 µg/m³, 3.4× usual Colorado Springs, 26 July: 16.3 µg/m³, 2.4× usual Colorado Springs, 27 July: 4.8 µg/m³, 0.7× usual Ken Caryl Ken Caryl, 17 July: 8.4 µg/m³, 1.4× usual Ken Caryl, 18 July: 9.8 µg/m³, 1.7× usual Ken Caryl, 19 July: 6.9 µg/m³, 1.2× usual Ken Caryl, 20 July: 7.6 µg/m³, 1.3× usual Ken Caryl, 21 July: 6.2 µg/m³, 1.1× usual Ken Caryl, 22 July: 21.8 µg/m³, 3.8× usual Ken Caryl, 23 July: 28.0 µg/m³, 4.8× usual Ken Caryl, 24 July: 26.3 µg/m³, 4.5× usual Ken Caryl, 25 July: 20.4 µg/m³, 3.5× usual Ken Caryl, 26 July: 11.2 µg/m³, 1.9× usual Ken Caryl, 27 July: 4.1 µg/m³, 0.7× usual Fort Collins Fort Collins, 17 July: 10.3 µg/m³, 1.6× usual Fort Collins, 18 July: 9.1 µg/m³, 1.4× usual Fort Collins, 19 July: 9.3 µg/m³, 1.5× usual Fort Collins, 20 July: 8.3 µg/m³, 1.3× usual Fort Collins, 21 July: 12.2 µg/m³, 1.9× usual Fort Collins, 22 July: 20.5 µg/m³, 3.3× usual Fort Collins, 23 July: 27.5 µg/m³, 4.4× usual Fort Collins, 24 July: 24.4 µg/m³, 3.9× usual Fort Collins, 25 July: 19.1 µg/m³, 3.0× usual Fort Collins, 26 July: 14.8 µg/m³, 2.3× usual Fort Collins, 27 July: 6.5 µg/m³, 1.0× usual Cheyenne Cheyenne, 17 July: 6.5 µg/m³, 1.3× usual Cheyenne, 18 July: 4.2 µg/m³, 0.8× usual Cheyenne, 19 July: 5.2 µg/m³, 1.0× usual Cheyenne, 20 July: 5.8 µg/m³, 1.2× usual Cheyenne, 21 July: 11.2 µg/m³, 2.2× usual Cheyenne, 22 July: 22.1 µg/m³, 4.4× usual Cheyenne, 23 July: 27.3 µg/m³, 5.5× usual Cheyenne, 24 July: 24.3 µg/m³, 4.9× usual Cheyenne, 25 July: 17.8 µg/m³, 3.6× usual Cheyenne, 26 July: 9.0 µg/m³, 1.8× usual Cheyenne, 27 July: 4.6 µg/m³, 0.9× usual Greeley Greeley, 17 July: 11.0 µg/m³, 1.5× usual Greeley, 18 July: 11.1 µg/m³, 1.5× usual Greeley, 19 July: 8.9 µg/m³, 1.2× usual Greeley, 20 July: 8.7 µg/m³, 1.2× usual Greeley, 21 July: 14.9 µg/m³, 2.0× usual Greeley, 22 July: 20.7 µg/m³, 2.8× usual Greeley, 23 July: 27.0 µg/m³, 3.6× usual Greeley, 24 July: 23.9 µg/m³, 3.2× usual Greeley, 25 July: 19.8 µg/m³, 2.7× usual Greeley, 26 July: 14.2 µg/m³, 1.9× usual Greeley, 27 July: 7.1 µg/m³, 1.0× usual Casper Casper, 17 July: 6.3 µg/m³, 1.3× usual Casper, 18 July: 7.9 µg/m³, 1.6× usual Casper, 19 July: 10.3 µg/m³, 2.1× usual Casper, 20 July: 6.3 µg/m³, 1.3× usual Casper, 21 July: no reading Casper, 22 July: no reading Casper, 23 July: 26.0 µg/m³, 5.2× usual Casper, 24 July: 15.8 µg/m³, 3.2× usual Casper, 25 July: 15.7 µg/m³, 3.1× usual Casper, 26 July: 4.2 µg/m³, 0.8× usual Casper, 27 July: 8.8 µg/m³, 1.8× usual Sheridan Sheridan, 17 July: 8.1 µg/m³, 1.2× usual Sheridan, 18 July: 16.4 µg/m³, 2.4× usual Sheridan, 19 July: 18.7 µg/m³, 2.7× usual Sheridan, 20 July: 10.7 µg/m³, 1.6× usual Sheridan, 21 July: 14.3 µg/m³, 2.1× usual Sheridan, 22 July: 24.8 µg/m³, 3.6× usual Sheridan, 23 July: 26.0 µg/m³, 3.8× usual Sheridan, 24 July: 16.9 µg/m³, 2.4× usual Sheridan, 25 July: 19.0 µg/m³, 2.8× usual Sheridan, 26 July: 13.2 µg/m³, 1.9× usual Sheridan, 27 July: 14.2 µg/m³, 2.1× usual 17 Jul 19 21 23 25 27 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
Sherwood Park Alberta, Canada 2 22 July 9.9 16× Prince Albert Saskatchewan, Canada 2 21 July 14.7 14× Lewiston Idaho, United States 1 26 July 8.3 13× St. Albert Alberta, Canada 3 20 July 9.3 13× Calgary Alberta, Canada 1 24 July 11.1 13× Edmonton Alberta, Canada 3 20 July 13.8 12× Saskatoon Saskatchewan, Canada 2 21 July 13.8 12× Red Deer Alberta, Canada 3 23 July 10.0 8.4× Regina Saskatchewan, Canada 2 22 July 12.2 6.5× Missoula Montana, United States 1 22 July 5.8 6.1× Swift Current Saskatchewan, Canada 2 22 July 9.9 6.0× Medicine Hat Alberta, Canada 3 21 July 9.0 5.7× Rapid City South Dakota, United States 2 21 July 8.8 5.6× Butte Montana, United States 1 27 July 6.9 5.5× Cheyenne Wyoming, United States 1 23 July 4.8 5.5× Gillette Wyoming, United States 2 23 July 6.6 5.4× Casper Wyoming, United States 1 23 July 5.0 5.2× Airdrie Alberta, Canada 1 24 July 8.1 5.2× Kamloops British Columbia, Canada 1 22 July 10.0 5.2× Ken Caryl Colorado, United States 2 23 July 5.8 4.8× Longmont Colorado, United States 2 23 July 7.2 4.8× Helena Montana, United States 2 22 July 9.3 4.6× Fort Collins Colorado, United States 1 23 July 6.3 4.4× Colorado Springs Colorado, United States 2 23 July 6.9 4.3× Thornton Colorado, United States 2 23 July 7.6 4.2× Great Falls Montana, United States 2 22 July 12.8 4.1× Cranbrook British Columbia, Canada 1 27 July 7.0 4.0× Billings Montana, United States 2 22 July 7.1 3.9× Lethbridge Alberta, Canada 1 22 July 8.3 3.9× Sheridan Wyoming, United States 1 23 July 6.9 3.8× Greeley Colorado, United States 1 23 July 7.4 3.6×
Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.
Against other episodes in the United States and Canada
Number 33 of 142 episodes in the United States and Canada since our records began, by cities reached.
North-eastern United States and Canada, June and July 2023 280 North-eastern United States and Canada, July 2026 264 North-eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, July and August 2025 241 North-eastern United States and Canada, July 2023 240 North-eastern United States and Canada, June 2025 196 North-eastern United States and Canada, June 2023 161 North-eastern United States and Canada, July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States, June 2025 104 North-western United States and Canada, August 2026 99 North-eastern United States and Canada, February 2026 96 North-western United States and Canada, July 2024 31 Bars: cities reached; colour: the level of the episode's highest daily reading. All 142 .
Use this page SmogRank, North-western United States and Canada, July 2024: 31 cities with PM2.5 at twice their usual or more, 20 to 24 July 2024, smogrank.com/episodes/2024-07-north-western-united-states-and-canada (accessed 3 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.
