SmogRank / Episodes / Canada
North-western Canada and United States, July 2024
For 3 days, from 23 to 25 July 2024, 17 cities in Canada and the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Calgary, Alberta, Canada: 139.5 µg/m³ on 24 July, about 12× its usual 11.3.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 17 in 2 countries
Days 3 23 to 25 July 2024
Worst day 24 July 11 cities counted
Furthest above usual 12× Sherwood Park
Day by day
Play 24 July 11 cities at twice their usual or more
Helena Bozeman Butte Billings Rexburg Cranbrook Idaho Falls Sheridan Conda Pocatello Coeur d'Alene Moscow Spokane Valley Pullman Spokane Gillette Casper Boise Great Falls Prince Albert Lethbridge Sherwood Park Lewiston Saskatoon Meridian Missoula Regina Nampa Airdrie Medicine Hat Swift Current Edmonton St. Albert Red Deer Calgary 20 Jul 21 22 23 24 25 26 27 28 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, 20 July: 170.0 µg/m³, 13× usual Edmonton, 21 July: 56.7 µg/m³, 4.3× usual Edmonton, 22 July: 66.3 µg/m³, 5.0× usual Edmonton, 23 July: 95.7 µg/m³, 7.2× usual Edmonton, 24 July: 61.3 µg/m³, 4.6× usual Edmonton, 25 July: 46.1 µg/m³, 3.5× usual Edmonton, 26 July: 13.8 µg/m³, 1.0× usual Edmonton, 27 July: 19.3 µg/m³, 1.5× usual Edmonton, 28 July: 17.3 µg/m³, 1.3× usual St. Albert St. Albert, 20 July: 120.0 µg/m³, 13× usual St. Albert, 21 July: 36.2 µg/m³, 4.0× usual St. Albert, 22 July: 48.3 µg/m³, 5.3× usual St. Albert, 23 July: 66.2 µg/m³, 7.3× usual St. Albert, 24 July: 36.7 µg/m³, 4.0× 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, 1.7× usual St. Albert, 28 July: 11.3 µg/m³, 1.2× usual Prince Albert 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, 5.3× usual Prince Albert, 23 July: 34.7 µg/m³, 2.4× usual Prince Albert, 24 July: 50.5 µg/m³, 3.5× 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 Prince Albert, 28 July: 44.0 µg/m³, 3.0× usual Sherwood Park Sherwood Park, 20 July: 44.2 µg/m³, 4.6× usual Sherwood Park, 21 July: no reading Sherwood Park, 22 July: 162.0 µg/m³, 17× usual Sherwood Park, 23 July: no reading Sherwood Park, 24 July: 32.7 µg/m³, 3.4× usual Sherwood Park, 25 July: 23.7 µg/m³, 2.5× usual Sherwood Park, 26 July: 9.5 µg/m³, 1.0× usual Sherwood Park, 27 July: 14.0 µg/m³, 1.5× usual Sherwood Park, 28 July: 13.0 µg/m³, 1.4× usual Red Deer 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 Red Deer, 28 July: 14.8 µg/m³, 1.5× usual Medicine Hat Medicine Hat, 20 July: 25.0 µg/m³, 2.8× usual Medicine Hat, 21 July: 51.6 µg/m³, 5.9× usual Medicine Hat, 22 July: 45.5 µg/m³, 5.2× usual Medicine Hat, 23 July: 49.1 µg/m³, 5.6× usual Medicine Hat, 24 July: 24.9 µg/m³, 2.8× usual Medicine Hat, 25 July: 33.5 µg/m³, 3.8× usual Medicine Hat, 26 July: 12.5 µg/m³, 1.4× usual Medicine Hat, 27 July: 17.6 µg/m³, 2.0× usual Medicine Hat, 28 July: 18.8 µg/m³, 2.1× usual Saskatoon Saskatoon, 20 July: 29.3 µg/m³, 2.2× usual Saskatoon, 21 July: 163.0 µg/m³, 12× usual Saskatoon, 22 July: 93.4 µg/m³, 7.1× usual Saskatoon, 23 July: 45.4 µg/m³, 3.4× usual Saskatoon, 24 July: 46.2 µg/m³, 3.5× usual Saskatoon, 25 July: 37.5 µg/m³, 2.8× usual Saskatoon, 26 July: 12.6 µg/m³, 1.0× usual Saskatoon, 27 July: 23.8 µg/m³, 1.8× usual Saskatoon, 28 July: 23.9 µg/m³, 1.8× usual Regina Regina, 20 July: 22.4 µg/m³, 1.9× usual Regina, 21 July: 49.4 µg/m³, 4.2× usual Regina, 22 July: 79.8 µg/m³, 6.8× usual Regina, 23 July: 48.8 µg/m³, 4.1× usual Regina, 24 July: 38.0 µg/m³, 3.2× usual Regina, 25 July: 29.3 µg/m³, 2.5× usual Regina, 26 July: 19.6 µg/m³, 1.7× usual Regina, 27 July: 12.1 µg/m³, 1.0× usual Regina, 28 July: 21.5 µg/m³, 1.8× usual Great Falls 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, 2.1× 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 Great Falls, 28 July: 21.3 µg/m³, 1.7× usual Swift Current 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 Swift Current, 28 July: 16.0 µg/m³, 1.6× usual Calgary 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, 4.9× usual Calgary, 24 July: 139.5 µg/m³, 12× usual Calgary, 25 July: 51.4 µg/m³, 4.5× usual Calgary, 26 July: 15.7 µg/m³, 1.4× usual Calgary, 27 July: 14.5 µg/m³, 1.3× usual Calgary, 28 July: 19.0 µg/m³, 1.7× usual Airdrie 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 Airdrie, 28 July: 24.4 µg/m³, 3.0× usual Missoula Missoula, 20 July: 17.5 µg/m³, 2.8× usual Missoula, 21 July: 19.9 µg/m³, 3.2× usual Missoula, 22 July: 35.2 µg/m³, 5.7× usual Missoula, 23 July: 24.0 µg/m³, 3.9× usual Missoula, 24 July: 25.5 µg/m³, 4.1× usual Missoula, 25 July: 23.2 µg/m³, 3.7× usual Missoula, 26 July: 13.2 µg/m³, 2.1× usual Missoula, 27 July: 17.0 µg/m³, 2.7× usual Missoula, 28 July: 17.9 µg/m³, 2.9× usual Lethbridge Lethbridge, 20 July: 10.3 µg/m³, 1.2× usual Lethbridge, 21 July: 16.1 µg/m³, 1.8× usual Lethbridge, 22 July: 32.1 µg/m³, 3.6× usual Lethbridge, 23 July: 21.6 µg/m³, 2.4× usual Lethbridge, 24 July: 17.6 µg/m³, 2.0× usual Lethbridge, 25 July: 27.0 µg/m³, 3.0× usual Lethbridge, 26 July: 10.1 µg/m³, 1.1× usual Lethbridge, 27 July: 19.2 µg/m³, 2.2× usual Lethbridge, 28 July: 19.6 µg/m³, 2.2× usual Lewiston Lewiston, 20 July: 13.3 µg/m³, 1.5× usual Lewiston, 21 July: 18.5 µg/m³, 2.1× usual Lewiston, 22 July: 25.3 µg/m³, 2.9× usual Lewiston, 23 July: 20.6 µg/m³, 2.4× usual Lewiston, 24 July: 29.5 µg/m³, 3.4× usual Lewiston, 25 July: 24.7 µg/m³, 2.8× usual Lewiston, 26 July: 109.9 µg/m³, 13× usual Lewiston, 27 July: 58.0 µg/m³, 6.7× usual Lewiston, 28 July: 50.3 µg/m³, 5.8× usual Nampa Nampa, 20 July: 19.8 µg/m³, 2.3× usual Nampa, 21 July: 14.8 µg/m³, 1.7× usual Nampa, 22 July: 14.0 µg/m³, 1.6× usual Nampa, 23 July: 99.7 µg/m³, 11× usual Nampa, 24 July: 42.7 µg/m³, 4.9× usual Nampa, 25 July: 39.6 µg/m³, 4.5× usual Nampa, 26 July: 49.3 µg/m³, 5.6× usual Nampa, 27 July: 66.7 µg/m³, 7.6× usual Nampa, 28 July: 42.5 µg/m³, 4.8× usual Meridian Meridian, 20 July: 22.0 µg/m³, 2.8× usual Meridian, 21 July: 17.1 µg/m³, 2.1× usual Meridian, 22 July: 16.0 µg/m³, 2.0× usual Meridian, 23 July: 93.6 µg/m³, 12× usual Meridian, 24 July: 30.0 µg/m³, 3.8× usual Meridian, 25 July: 38.1 µg/m³, 4.8× usual Meridian, 26 July: 46.2 µg/m³, 5.8× usual Meridian, 27 July: 68.8 µg/m³, 8.6× usual Meridian, 28 July: 47.7 µg/m³, 6.0× usual 20 Jul 21 22 23 24 25 26 27 28 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 1 22 July 9.6 17× Prince Albert Saskatchewan, Canada 2 21 July 14.5 14× St. Albert Alberta, Canada 3 20 July 9.1 13× Edmonton Alberta, Canada 3 20 July 13.3 13× Lewiston Idaho, United States 1 26 July 8.7 13× Saskatoon Saskatchewan, Canada 2 21 July 13.2 12× Calgary Alberta, Canada 3 24 July 11.3 12× Meridian Idaho, United States 1 23 July 8.0 12× Nampa Idaho, United States 1 23 July 8.8 11× Red Deer Alberta, Canada 2 23 July 10.0 8.4× Regina Saskatchewan, Canada 2 22 July 11.8 6.8× Swift Current Saskatchewan, Canada 2 22 July 9.9 6.0× Medicine Hat Alberta, Canada 2 21 July 8.8 5.9× Missoula Montana, United States 1 22 July 6.2 5.7× Airdrie Alberta, Canada 3 24 July 8.1 5.2× Great Falls Montana, United States 1 22 July 12.9 4.1× Lethbridge Alberta, Canada 1 22 July 8.9 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 Canada and the United States
Number 63 of 142 episodes in Canada and the United States 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 Canada and United States, July 2024 17 Bars: cities reached; colour: the level of the episode's highest daily reading. All 142 .
Use this page SmogRank, North-western Canada and United States, July 2024: 17 cities with PM2.5 at twice their usual or more, 23 to 25 July 2024, smogrank.com/episodes/2024-07-north-western-canada-and-united-states (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.
