SmogRank / Episodes / Canada

North-western Canada and United States, 12 to 13 May 2024

For 2 days, from 12 to 13 May 2024, 13 cities in Canada and the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Grande Prairie, Alberta, Canada: 208.0 µg/m³ on 12 May, about 42× its usual 4.4. Ended 13 May.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached13in 2 countries
Days212 to 13 May 2024
Worst day12 May13 cities counted
Furthest above usual42×Grande Prairie

Day by day

12 May 13 cities at twice their usual or more
CranbrookColumbia FallsCastlegarSandpointGrand CentreVernonKelownaPentictonKamloopsMedicine HatAirdrieLethbridgeHavreCalgaryRed DeerSt. AlbertSherwood ParkEdmontonFort SaskatchewanDrayton ValleyEdsonGrande Prairie
9 May10111213141516
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

Grande PrairieGrande Prairie, 9 May: 2.9 µg/m³Grande Prairie, 10 May: 3.9 µg/m³Grande Prairie, 11 May: 603.0 µg/m³Grande Prairie, 12 May: 208.0 µg/m³, 42× its usual 4.4Grande Prairie, 13 May: 3.3 µg/m³Grande Prairie, 14 May: 2.4 µg/m³Grande Prairie, 15 May: 1.0 µg/m³Grande Prairie, 16 May: 6.1 µg/m³EdmontonEdmonton, 9 May: 4.7 µg/m³Edmonton, 10 May: 7.6 µg/m³Edmonton, 11 May: 163.0 µg/m³Edmonton, 12 May: 128.0 µg/m³, 18× its usual 7.0Edmonton, 13 May: 26.9 µg/m³, 3.7× its usual 7.3Edmonton, 14 May: 4.1 µg/m³Edmonton, 15 May: 3.7 µg/m³Edmonton, 16 May: 4.9 µg/m³EdsonEdson, 9 May: 4.1 µg/m³Edson, 10 May: 5.1 µg/m³Edson, 11 May: 185.0 µg/m³Edson, 12 May: 113.0 µg/m³, 21× its usual 5.5Edson, 13 May: 2.9 µg/m³Edson, 14 May: 0.9 µg/m³Edson, 15 May: 1.3 µg/m³Edson, 16 May: 3.3 µg/m³Fort SaskatchewanFort Saskatchewan, 9 May: 4.7 µg/m³Fort Saskatchewan, 10 May: 6.1 µg/m³Fort Saskatchewan, 11 May: 150.0 µg/m³Fort Saskatchewan, 12 May: 113.0 µg/m³, 19× its usual 6.1Fort Saskatchewan, 13 May: 27.0 µg/m³, 4.4× its usual 6.1Fort Saskatchewan, 14 May: 4.1 µg/m³Fort Saskatchewan, 15 May: 2.8 µg/m³Fort Saskatchewan, 16 May: 5.4 µg/m³Drayton ValleyDrayton Valley, 9 May: 5.2 µg/m³Drayton Valley, 10 May: 5.6 µg/m³Drayton Valley, 11 May: 137.0 µg/m³Drayton Valley, 12 May: 99.5 µg/m³, 19× its usual 5.2Drayton Valley, 13 May: 11.4 µg/m³Drayton Valley, 14 May: 2.4 µg/m³Drayton Valley, 15 May: 2.0 µg/m³Drayton Valley, 16 May: 4.0 µg/m³St. AlbertSt. Albert, 9 May: 3.1 µg/m³St. Albert, 10 May: 6.6 µg/m³St. Albert, 11 May: 114.0 µg/m³St. Albert, 12 May: 85.1 µg/m³, 15× its usual 5.5St. Albert, 13 May: 15.9 µg/m³St. Albert, 14 May: 0.9 µg/m³St. Albert, 15 May: 0.4 µg/m³St. Albert, 16 May: 3.1 µg/m³Red DeerRed Deer, 9 May: 4.9 µg/m³Red Deer, 10 May: 4.9 µg/m³Red Deer, 11 May: 89.8 µg/m³Red Deer, 12 May: 81.7 µg/m³, 14× its usual 5.7Red Deer, 13 May: 26.3 µg/m³, 4.4× its usual 6.0Red Deer, 14 May: 2.3 µg/m³Red Deer, 15 May: 3.7 µg/m³Red Deer, 16 May: 3.3 µg/m³Sherwood ParkSherwood Park, 9 May: 5.3 µg/m³Sherwood Park, 10 May: 5.7 µg/m³Sherwood Park, 11 May: 98.7 µg/m³Sherwood Park, 12 May: 79.8 µg/m³, 16× its usual 4.8Sherwood Park, 13 May: 19.5 µg/m³Sherwood Park, 14 May: no readingSherwood Park, 15 May: no readingSherwood Park, 16 May: 3.8 µg/m³CalgaryCalgary, 9 May: 6.8 µg/m³Calgary, 10 May: 6.3 µg/m³Calgary, 11 May: 38.6 µg/m³Calgary, 12 May: 58.0 µg/m³, 8.9× its usual 6.5Calgary, 13 May: 27.1 µg/m³, 4.2× its usual 6.4Calgary, 14 May: 5.2 µg/m³Calgary, 15 May: 5.1 µg/m³Calgary, 16 May: 4.5 µg/m³HavreHavre, 9 May: 3.1 µg/m³Havre, 10 May: 2.9 µg/m³Havre, 11 May: 3.8 µg/m³Havre, 12 May: 44.6 µg/m³, 8.9× its usual 3.2Havre, 13 May: 8.7 µg/m³Havre, 14 May: 8.6 µg/m³Havre, 15 May: 5.2 µg/m³Havre, 16 May: 2.9 µg/m³LethbridgeLethbridge, 9 May: 3.9 µg/m³Lethbridge, 10 May: 4.1 µg/m³Lethbridge, 11 May: 15.7 µg/m³Lethbridge, 12 May: 39.9 µg/m³, 8.0× its usual 4.4Lethbridge, 13 May: 19.4 µg/m³Lethbridge, 14 May: 4.5 µg/m³Lethbridge, 15 May: 2.5 µg/m³Lethbridge, 16 May: 3.6 µg/m³AirdrieAirdrie, 9 May: 3.7 µg/m³Airdrie, 10 May: 3.9 µg/m³Airdrie, 11 May: 47.3 µg/m³Airdrie, 12 May: 39.3 µg/m³, 7.9× its usual 4.5Airdrie, 13 May: 17.7 µg/m³Airdrie, 14 May: 1.0 µg/m³Airdrie, 15 May: 1.3 µg/m³Airdrie, 16 May: 1.0 µg/m³Medicine HatMedicine Hat, 9 May: 2.7 µg/m³Medicine Hat, 10 May: 2.5 µg/m³Medicine Hat, 11 May: 24.2 µg/m³Medicine Hat, 12 May: 31.9 µg/m³, 6.4× its usual 4.2Medicine Hat, 13 May: 10.8 µg/m³Medicine Hat, 14 May: 9.4 µg/m³Medicine Hat, 15 May: 3.7 µg/m³Medicine Hat, 16 May: 2.3 µg/m³9 May10111213141516
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
Grande PrairieAlberta, Canada1 208.012 May4.442×
EdsonAlberta, Canada1 113.012 May5.521×
Drayton ValleyAlberta, Canada1 99.512 May5.219×
Fort SaskatchewanAlberta, Canada2 113.012 May6.119×
EdmontonAlberta, Canada2 128.012 May7.018×
Sherwood ParkAlberta, Canada1 79.812 May4.816×
St. AlbertAlberta, Canada1 85.112 May5.516×
Red DeerAlberta, Canada2 81.712 May5.714×
CalgaryAlberta, Canada2 58.012 May6.58.9×
HavreMontana, United States1 44.612 May3.28.9×
LethbridgeAlberta, Canada1 39.912 May4.48.0×
AirdrieAlberta, Canada1 39.312 May4.57.9×
Medicine HatAlberta, Canada1 31.912 May4.26.4×

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 Canada and the United States

Number 102 of 173 episodes in Canada and the United States since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 173.

Use this page

SmogRank, North-western Canada and United States, 12 to 13 May 2024: 13 cities with PM2.5 at twice their usual or more, 12 to 13 May 2024, smogrank.com/episodes/2024-05-12-north-western-canada-and-united-states (accessed 5 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.