SmogRank / Episodes / Canada
North-western Canada and United States, July 2023
For 3 days, from 15 to 17 July 2023, 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 Edmonton, Alberta, Canada: 202.0 µg/m³ on 15 July, about 17× its usual 12.1.
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 15 to 17 July 2023
Worst day 15 July 17 cities counted
Furthest above usual 19× Swift Current
Day by day
Play 15 July 17 cities at twice their usual or more
Helena Butte Missoula Bozeman Sherwood Park Rexburg Coeur d'Alene Idaho Falls Spokane Valley Moscow Spokane Lewiston Pullman Sheridan Boise Meridian Walla Walla Nampa Prince Albert Moses Lake Pendleton Kelowna Pasco Penticton Tri-Cities Hermiston Sunnyside Wenatchee Ellensburg Yakima The Dalles Redmond Bend Regina Saskatoon Great Falls Calgary Billings Vernon Cranbrook Airdrie Gillette Rapid City Lethbridge Kamloops Red Deer St. Albert Medicine Hat Edmonton Swift Current 12 Jul 13 14 15 16 17 18 19 20 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, 12 July: 35.1 µg/m³, 2.9× usual Edmonton, 13 July: 75.9 µg/m³, 6.3× usual Edmonton, 14 July: no reading Edmonton, 15 July: 202.0 µg/m³, 17× usual Edmonton, 16 July: 111.0 µg/m³, 9.2× usual Edmonton, 17 July: 45.7 µg/m³, 3.8× usual Edmonton, 18 July: 25.7 µg/m³, 2.1× usual Edmonton, 19 July: 22.8 µg/m³, 1.9× usual Edmonton, 20 July: 42.3 µg/m³, 3.5× usual Red Deer Red Deer, 12 July: 32.2 µg/m³, 3.4× usual Red Deer, 13 July: 60.5 µg/m³, 6.4× usual Red Deer, 14 July: no reading Red Deer, 15 July: 91.9 µg/m³, 9.8× usual Red Deer, 16 July: 57.7 µg/m³, 6.1× usual Red Deer, 17 July: 29.3 µg/m³, 3.1× usual Red Deer, 18 July: 10.8 µg/m³, 1.1× usual Red Deer, 19 July: 16.8 µg/m³, 1.8× usual Red Deer, 20 July: 17.3 µg/m³, 1.8× usual Airdrie Airdrie, 12 July: 16.0 µg/m³, 2.2× usual Airdrie, 13 July: 57.4 µg/m³, 7.9× usual Airdrie, 14 July: no reading Airdrie, 15 July: 40.8 µg/m³, 5.6× usual Airdrie, 16 July: 41.1 µg/m³, 5.6× usual Airdrie, 17 July: 36.4 µg/m³, 5.0× usual Airdrie, 18 July: 8.3 µg/m³, 1.1× usual Airdrie, 19 July: 13.7 µg/m³, 1.9× usual Airdrie, 20 July: 13.7 µg/m³, 1.9× usual Calgary Calgary, 12 July: 16.4 µg/m³, 1.6× usual Calgary, 13 July: 55.3 µg/m³, 5.5× usual Calgary, 14 July: no reading Calgary, 15 July: 49.9 µg/m³, 4.9× usual Calgary, 16 July: 47.1 µg/m³, 4.7× usual Calgary, 17 July: 42.2 µg/m³, 4.2× usual Calgary, 18 July: 6.3 µg/m³, 0.6× usual Calgary, 19 July: 15.9 µg/m³, 1.6× usual Calgary, 20 July: 17.1 µg/m³, 1.7× usual Saskatoon Saskatoon, 12 July: 9.3 µg/m³, 0.7× usual Saskatoon, 13 July: 39.1 µg/m³, 3.1× usual Saskatoon, 14 July: no reading Saskatoon, 15 July: 46.3 µg/m³, 3.7× usual Saskatoon, 16 July: 19.5 µg/m³, 1.5× usual Saskatoon, 17 July: 9.4 µg/m³, 0.7× usual Saskatoon, 18 July: 12.2 µg/m³, 1.0× usual Saskatoon, 19 July: 23.1 µg/m³, 1.8× usual Saskatoon, 20 July: 30.0 µg/m³, 2.4× usual St. Albert St. Albert, 12 July: 21.9 µg/m³, 2.5× usual St. Albert, 13 July: 38.4 µg/m³, 4.4× usual St. Albert, 14 July: no reading St. Albert, 15 July: 112.0 µg/m³, 13× usual St. Albert, 16 July: 50.3 µg/m³, 5.7× usual St. Albert, 17 July: 23.3 µg/m³, 2.6× usual St. Albert, 18 July: 8.7 µg/m³, 1.0× usual St. Albert, 19 July: 12.2 µg/m³, 1.4× usual St. Albert, 20 July: 24.7 µg/m³, 2.8× usual Swift Current Swift Current, 12 July: 6.4 µg/m³, 0.8× usual Swift Current, 13 July: 29.6 µg/m³, 3.5× usual Swift Current, 14 July: no reading Swift Current, 15 July: 159.0 µg/m³, 19× usual Swift Current, 16 July: 65.2 µg/m³, 7.7× usual Swift Current, 17 July: 24.3 µg/m³, 2.9× usual Swift Current, 18 July: 18.1 µg/m³, 2.1× usual Swift Current, 19 July: 17.7 µg/m³, 2.1× usual Swift Current, 20 July: 19.9 µg/m³, 2.3× usual Medicine Hat Medicine Hat, 12 July: 9.0 µg/m³, 1.3× usual Medicine Hat, 13 July: 29.1 µg/m³, 4.1× usual Medicine Hat, 14 July: no reading Medicine Hat, 15 July: 70.7 µg/m³, 10.0× usual Medicine Hat, 16 July: 92.0 µg/m³, 13× usual Medicine Hat, 17 July: 30.4 µg/m³, 4.3× usual Medicine Hat, 18 July: 3.5 µg/m³, 0.5× usual Medicine Hat, 19 July: 9.8 µg/m³, 1.4× usual Medicine Hat, 20 July: 12.1 µg/m³, 1.7× usual Regina Regina, 12 July: 6.4 µg/m³, 0.5× usual Regina, 13 July: 25.3 µg/m³, 2.1× usual Regina, 14 July: no reading Regina, 15 July: 32.9 µg/m³, 2.8× usual Regina, 16 July: 10.9 µg/m³, 0.9× usual Regina, 17 July: 5.8 µg/m³, 0.5× usual Regina, 18 July: 16.5 µg/m³, 1.4× usual Regina, 19 July: 11.8 µg/m³, 1.0× usual Regina, 20 July: 22.6 µg/m³, 1.9× usual Billings Billings, 12 July: 5.3 µg/m³, 0.7× usual Billings, 13 July: 5.4 µg/m³, 0.8× usual Billings, 14 July: 29.0 µg/m³, 4.0× usual Billings, 15 July: 37.6 µg/m³, 5.2× usual Billings, 16 July: 31.2 µg/m³, 4.3× usual Billings, 17 July: 43.7 µg/m³, 6.1× usual Billings, 18 July: no reading Billings, 19 July: 10.4 µg/m³, 1.4× usual Billings, 20 July: 13.4 µg/m³, 1.9× usual Rapid City Rapid City, 12 July: 12.0 µg/m³, 1.4× usual Rapid City, 13 July: 9.7 µg/m³, 1.2× usual Rapid City, 14 July: 26.5 µg/m³, 3.2× usual Rapid City, 15 July: 47.1 µg/m³, 5.6× usual Rapid City, 16 July: 55.4 µg/m³, 6.6× usual Rapid City, 17 July: 51.6 µg/m³, 6.1× usual Rapid City, 18 July: 16.3 µg/m³, 1.9× usual Rapid City, 19 July: 13.6 µg/m³, 1.6× usual Rapid City, 20 July: 14.9 µg/m³, 1.8× usual Kamloops Kamloops, 12 July: 8.5 µg/m³, 1.0× usual Kamloops, 13 July: 13.9 µg/m³, 1.7× usual Kamloops, 14 July: no reading Kamloops, 15 July: 76.2 µg/m³, 9.1× usual Kamloops, 16 July: 8.8 µg/m³, 1.0× usual Kamloops, 17 July: 6.6 µg/m³, 0.8× usual Kamloops, 18 July: 7.5 µg/m³, 0.9× usual Kamloops, 19 July: 8.8 µg/m³, 1.0× usual Kamloops, 20 July: 9.1 µg/m³, 1.1× usual Lethbridge Lethbridge, 12 July: no reading Lethbridge, 13 July: 19.4 µg/m³, 2.6× usual Lethbridge, 14 July: no reading Lethbridge, 15 July: 46.9 µg/m³, 6.2× usual Lethbridge, 16 July: 51.9 µg/m³, 6.8× usual Lethbridge, 17 July: 17.1 µg/m³, 2.3× usual Lethbridge, 18 July: 5.6 µg/m³, 0.7× usual Lethbridge, 19 July: 12.6 µg/m³, 1.7× usual Lethbridge, 20 July: 13.2 µg/m³, 1.7× usual Great Falls Great Falls, 12 July: 16.5 µg/m³, 1.4× usual Great Falls, 13 July: 14.8 µg/m³, 1.2× usual Great Falls, 14 July: no reading Great Falls, 15 July: 44.8 µg/m³, 3.7× usual Great Falls, 16 July: 27.4 µg/m³, 2.3× usual Great Falls, 17 July: 15.2 µg/m³, 1.3× usual Great Falls, 18 July: 8.9 µg/m³, 0.7× usual Great Falls, 19 July: 15.7 µg/m³, 1.3× usual Great Falls, 20 July: 19.2 µg/m³, 1.6× usual Gillette Gillette, 12 July: 7.5 µg/m³, 1.3× usual Gillette, 13 July: 7.7 µg/m³, 1.3× usual Gillette, 14 July: 20.0 µg/m³, 3.4× usual Gillette, 15 July: 35.7 µg/m³, 6.1× usual Gillette, 16 July: 32.7 µg/m³, 5.5× usual Gillette, 17 July: 43.6 µg/m³, 7.4× usual Gillette, 18 July: no reading Gillette, 19 July: 8.7 µg/m³, 1.5× usual Gillette, 20 July: 11.6 µg/m³, 2.0× usual Cranbrook Cranbrook, 12 July: 13.4 µg/m³, 2.1× usual Cranbrook, 13 July: 11.6 µg/m³, 1.8× usual Cranbrook, 14 July: no reading Cranbrook, 15 July: 34.7 µg/m³, 5.5× usual Cranbrook, 16 July: 5.5 µg/m³, 0.9× usual Cranbrook, 17 July: 4.9 µg/m³, 0.8× usual Cranbrook, 18 July: 9.4 µg/m³, 1.5× usual Cranbrook, 19 July: 20.7 µg/m³, 3.3× usual Cranbrook, 20 July: 88.6 µg/m³, 14× usual Vernon Vernon, 12 July: 15.9 µg/m³, 2.5× usual Vernon, 13 July: 8.4 µg/m³, 1.3× usual Vernon, 14 July: no reading Vernon, 15 July: 33.1 µg/m³, 5.3× usual Vernon, 16 July: 3.4 µg/m³, 0.5× usual Vernon, 17 July: 2.4 µg/m³, 0.4× usual Vernon, 18 July: 6.9 µg/m³, 1.1× usual Vernon, 19 July: 8.7 µg/m³, 1.4× usual Vernon, 20 July: 6.5 µg/m³, 1.0× usual 12 Jul 13 14 15 16 17 18 19 20 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
Swift Current Saskatchewan, Canada 2 15 July 8.5 19× Edmonton Alberta, Canada 3 15 July 12.1 17× Cranbrook British Columbia, Canada 1 20 July 6.3 14× Medicine Hat Alberta, Canada 3 16 July 7.1 13× St. Albert Alberta, Canada 2 15 July 8.8 13× Red Deer Alberta, Canada 3 15 July 9.4 9.8× Kamloops British Columbia, Canada 1 15 July 8.4 9.1× Airdrie Alberta, Canada 3 13 July 7.3 7.9× Gillette Wyoming, United States 2 17 July 5.9 7.4× Lethbridge Alberta, Canada 2 16 July 7.6 6.8× Rapid City South Dakota, United States 2 16 July 8.4 6.6× Billings Montana, United States 2 17 July 7.2 6.1× Calgary Alberta, Canada 3 13 July 10.1 5.5× Vernon British Columbia, Canada 1 15 July 6.3 5.3× Great Falls Montana, United States 2 15 July 12.1 3.7× Saskatoon Saskatchewan, Canada 1 15 July 12.6 3.7× Regina Saskatchewan, Canada 1 15 July 11.8 2.8×
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 22 of 45 episodes in Canada and the United States since our records began, by cities reached.
North-eastern United States and Canada, June and July 2023 279 North-eastern United States and Canada, May and June 2023 260 North-eastern United States and Canada, July 2023 241 North-eastern United States and Canada, June 2023 161 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, July 2023 75 Western United States, September 2023 61 South-eastern United States, October 2023 47 North-eastern United States, July 2023 46 North-western United States and Canada, May 2023 42 Western United States, December 2023 32 Northern United States, January 2023 32 North-western Canada and United States, July 2023 17 Bars: cities reached; colour: the level of the episode's highest daily reading. All 45 .
Use this page SmogRank, North-western Canada and United States, July 2023: 17 cities with PM2.5 at twice their usual or more, 15 to 17 July 2023, smogrank.com/episodes/2023-07-north-western-canada-and-united-states (accessed 2 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.
