SmogRank / Episodes / United States
Northern United States, May 2024
For 3 days, from 12 to 14 May 2024, 25 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Rochester, Minnesota, United States: 61.8 µg/m³ on 13 May, about 10× its usual 5.9.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 25 in 2 countries
Days 3 12 to 14 May 2024
Worst day 13 May 15 cities counted
Furthest above usual 11× Eau Claire
Day by day
Play 13 May 15 cities at twice their usual or more
Ankeny Des Moines Iowa City Muscatine Davenport Moline Clinton Madison Saint Joseph Rockford Peoria Columbia Liberty Kansas City Springfield Raymore Bloomington Sioux Falls Olathe Lincoln Upper Alton Cary Waukesha University City Naperville Decatur Granite City St. Louis East Saint Louis Lemay Joliet Arnold Milwaukee Des Plaines South Milwaukee Zion Franklin Park Northbrook Brookfield Oak Lawn Champaign Chicago Calumet City Hammond East Chicago Springfield Gary Portage Terre Haute Springdale Marquette Paducah Evansville Tulsa Dyersburg Jenks Clarksville Waterloo Kansas City Omaha Derby Brookings Watertown Ponca City Bellevue Green Bay Appleton Topeka Superior Saint Cloud Duluth West Fargo Thunder Bay Saint Michael Saint Paul Minneapolis Shakopee Blaine Apple Valley Rochester Burnsville Eau Claire 9 May 10 11 12 13 14 15 16 17 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
West Fargo West Fargo, 9 May: 4.0 µg/m³, 0.7× usual West Fargo, 10 May: 5.9 µg/m³, 1.0× usual West Fargo, 11 May: 9.7 µg/m³, 1.6× usual West Fargo, 12 May: 48.1 µg/m³, 8.0× usual West Fargo, 13 May: 14.3 µg/m³, 2.4× usual West Fargo, 14 May: 11.0 µg/m³, 1.8× usual West Fargo, 15 May: 5.0 µg/m³, 0.8× usual West Fargo, 16 May: no reading West Fargo, 17 May: no reading Thunder Bay Thunder Bay, 9 May: 3.0 µg/m³, 0.6× usual Thunder Bay, 10 May: 4.9 µg/m³, 1.0× usual Thunder Bay, 11 May: 3.3 µg/m³, 0.7× usual Thunder Bay, 12 May: 40.7 µg/m³, 8.1× usual Thunder Bay, 13 May: 10.9 µg/m³, 2.2× usual Thunder Bay, 14 May: 2.9 µg/m³, 0.6× usual Thunder Bay, 15 May: 5.8 µg/m³, 1.2× usual Thunder Bay, 16 May: 5.0 µg/m³, 1.0× usual Thunder Bay, 17 May: 3.5 µg/m³, 0.7× usual Duluth Duluth, 9 May: 1.5 µg/m³, 0.3× usual Duluth, 10 May: 2.8 µg/m³, 0.6× usual Duluth, 11 May: 3.7 µg/m³, 0.7× usual Duluth, 12 May: 37.2 µg/m³, 7.4× usual Duluth, 13 May: 19.8 µg/m³, 4.0× usual Duluth, 14 May: 2.0 µg/m³, 0.4× usual Duluth, 15 May: 1.8 µg/m³, 0.4× usual Duluth, 16 May: 4.8 µg/m³, 1.0× usual Duluth, 17 May: 4.5 µg/m³, 0.9× usual Superior Superior, 9 May: 1.6 µg/m³, 0.3× usual Superior, 10 May: 2.8 µg/m³, 0.6× usual Superior, 11 May: 4.1 µg/m³, 0.8× usual Superior, 12 May: 36.2 µg/m³, 7.2× usual Superior, 13 May: 21.7 µg/m³, 4.3× usual Superior, 14 May: 2.9 µg/m³, 0.6× usual Superior, 15 May: 2.2 µg/m³, 0.4× usual Superior, 16 May: 4.4 µg/m³, 0.9× usual Superior, 17 May: 5.2 µg/m³, 1.0× usual Saint Michael Saint Michael, 9 May: 2.1 µg/m³, 0.4× usual Saint Michael, 10 May: 4.7 µg/m³, 0.9× usual Saint Michael, 11 May: 6.1 µg/m³, 1.2× usual Saint Michael, 12 May: 33.8 µg/m³, 6.8× usual Saint Michael, 13 May: 42.0 µg/m³, 8.4× usual Saint Michael, 14 May: 9.9 µg/m³, 2.0× usual Saint Michael, 15 May: 11.3 µg/m³, 2.3× usual Saint Michael, 16 May: 7.5 µg/m³, 1.5× usual Saint Michael, 17 May: 9.2 µg/m³, 1.8× usual Saint Cloud Saint Cloud, 9 May: 1.7 µg/m³, 0.3× usual Saint Cloud, 10 May: 4.1 µg/m³, 0.8× usual Saint Cloud, 11 May: 5.3 µg/m³, 1.0× usual Saint Cloud, 12 May: 29.0 µg/m³, 5.7× usual Saint Cloud, 13 May: 37.1 µg/m³, 7.3× usual Saint Cloud, 14 May: 8.2 µg/m³, 1.6× usual Saint Cloud, 15 May: 10.1 µg/m³, 2.0× usual Saint Cloud, 16 May: 6.5 µg/m³, 1.3× usual Saint Cloud, 17 May: 8.4 µg/m³, 1.6× usual Watertown Watertown, 9 May: 4.3 µg/m³, 0.6× usual Watertown, 10 May: 7.0 µg/m³, 1.0× usual Watertown, 11 May: 7.2 µg/m³, 1.1× usual Watertown, 12 May: 26.0 µg/m³, 3.9× usual Watertown, 13 May: 33.7 µg/m³, 5.0× usual Watertown, 14 May: 14.3 µg/m³, 2.1× usual Watertown, 15 May: 15.6 µg/m³, 2.3× usual Watertown, 16 May: 13.3 µg/m³, 2.0× usual Watertown, 17 May: 9.7 µg/m³, 1.4× usual Blaine Blaine, 9 May: 2.4 µg/m³, 0.5× usual Blaine, 10 May: 4.0 µg/m³, 0.8× usual Blaine, 11 May: 6.1 µg/m³, 1.2× usual Blaine, 12 May: 25.8 µg/m³, 5.2× usual Blaine, 13 May: 48.1 µg/m³, 9.6× usual Blaine, 14 May: 9.1 µg/m³, 1.8× usual Blaine, 15 May: 11.0 µg/m³, 2.2× usual Blaine, 16 May: 9.3 µg/m³, 1.9× usual Blaine, 17 May: 8.8 µg/m³, 1.8× usual Saint Paul Saint Paul, 9 May: no reading Saint Paul, 10 May: 4.3 µg/m³, 0.8× usual Saint Paul, 11 May: 6.3 µg/m³, 1.1× usual Saint Paul, 12 May: 25.0 µg/m³, 4.4× usual Saint Paul, 13 May: 49.2 µg/m³, 8.6× usual Saint Paul, 14 May: 11.4 µg/m³, 2.0× usual Saint Paul, 15 May: 10.1 µg/m³, 1.8× usual Saint Paul, 16 May: 11.2 µg/m³, 2.0× usual Saint Paul, 17 May: 8.9 µg/m³, 1.6× usual Rochester Rochester, 9 May: 3.5 µg/m³, 0.6× usual Rochester, 10 May: 4.6 µg/m³, 0.8× usual Rochester, 11 May: 8.9 µg/m³, 1.5× usual Rochester, 12 May: 7.3 µg/m³, 1.2× usual Rochester, 13 May: 61.8 µg/m³, 10× usual Rochester, 14 May: 22.0 µg/m³, 3.7× usual Rochester, 15 May: 17.2 µg/m³, 2.9× usual Rochester, 16 May: 12.6 µg/m³, 2.1× usual Rochester, 17 May: 12.7 µg/m³, 2.2× usual Burnsville Burnsville, 9 May: 3.4 µg/m³, 0.6× usual Burnsville, 10 May: 4.4 µg/m³, 0.8× usual Burnsville, 11 May: 7.8 µg/m³, 1.4× usual Burnsville, 12 May: 21.2 µg/m³, 3.9× usual Burnsville, 13 May: 59.6 µg/m³, 11× usual Burnsville, 14 May: 16.2 µg/m³, 2.9× usual Burnsville, 15 May: 14.4 µg/m³, 2.6× usual Burnsville, 16 May: 12.2 µg/m³, 2.2× usual Burnsville, 17 May: no reading Eau Claire Eau Claire, 9 May: 2.7 µg/m³, 0.5× usual Eau Claire, 10 May: 2.9 µg/m³, 0.6× usual Eau Claire, 11 May: 4.3 µg/m³, 0.8× usual Eau Claire, 12 May: 11.1 µg/m³, 2.2× usual Eau Claire, 13 May: 56.0 µg/m³, 11× usual Eau Claire, 14 May: 15.4 µg/m³, 3.0× usual Eau Claire, 15 May: 6.8 µg/m³, 1.3× usual Eau Claire, 16 May: 9.2 µg/m³, 1.8× usual Eau Claire, 17 May: 9.5 µg/m³, 1.9× usual Shakopee Shakopee, 9 May: 2.7 µg/m³, 0.5× usual Shakopee, 10 May: 4.3 µg/m³, 0.7× usual Shakopee, 11 May: 6.0 µg/m³, 1.0× usual Shakopee, 12 May: 24.7 µg/m³, 4.1× usual Shakopee, 13 May: 53.7 µg/m³, 9.0× usual Shakopee, 14 May: 15.1 µg/m³, 2.5× usual Shakopee, 15 May: 13.3 µg/m³, 2.2× usual Shakopee, 16 May: 9.6 µg/m³, 1.6× usual Shakopee, 17 May: 9.1 µg/m³, 1.5× usual Apple Valley Apple Valley, 9 May: 3.0 µg/m³, 0.6× usual Apple Valley, 10 May: 3.7 µg/m³, 0.7× usual Apple Valley, 11 May: 5.4 µg/m³, 1.0× usual Apple Valley, 12 May: 18.5 µg/m³, 3.4× usual Apple Valley, 13 May: 53.5 µg/m³, 9.9× usual Apple Valley, 14 May: 15.1 µg/m³, 2.8× usual Apple Valley, 15 May: 14.1 µg/m³, 2.6× usual Apple Valley, 16 May: 10.2 µg/m³, 1.9× usual Apple Valley, 17 May: 11.6 µg/m³, 2.1× usual Minneapolis Minneapolis, 9 May: 3.0 µg/m³, 0.5× usual Minneapolis, 10 May: 5.2 µg/m³, 0.9× usual Minneapolis, 11 May: 6.1 µg/m³, 1.1× usual Minneapolis, 12 May: 22.9 µg/m³, 3.9× usual Minneapolis, 13 May: 51.2 µg/m³, 8.8× usual Minneapolis, 14 May: 11.2 µg/m³, 1.9× usual Minneapolis, 15 May: 12.4 µg/m³, 2.1× usual Minneapolis, 16 May: 9.9 µg/m³, 1.7× usual Minneapolis, 17 May: 9.4 µg/m³, 1.6× usual Appleton Appleton, 9 May: 3.1 µg/m³, 0.6× usual Appleton, 10 May: 2.2 µg/m³, 0.4× usual Appleton, 11 May: 2.8 µg/m³, 0.6× usual Appleton, 12 May: 5.3 µg/m³, 1.1× usual Appleton, 13 May: 33.9 µg/m³, 6.8× usual Appleton, 14 May: 1.7 µg/m³, 0.3× usual Appleton, 15 May: 4.4 µg/m³, 0.9× usual Appleton, 16 May: 9.7 µg/m³, 1.9× usual Appleton, 17 May: 7.1 µg/m³, 1.4× usual Brookings Brookings, 9 May: 2.4 µg/m³, 0.3× usual Brookings, 10 May: 6.5 µg/m³, 0.9× usual Brookings, 11 May: 7.7 µg/m³, 1.1× usual Brookings, 12 May: 19.0 µg/m³, 2.7× usual Brookings, 13 May: 33.5 µg/m³, 4.7× usual Brookings, 14 May: 10.9 µg/m³, 1.5× usual Brookings, 15 May: 14.1 µg/m³, 2.0× usual Brookings, 16 May: 11.3 µg/m³, 1.6× usual Brookings, 17 May: 10.0 µg/m³, 1.4× usual Green Bay Green Bay, 9 May: 2.6 µg/m³, 0.5× usual Green Bay, 10 May: 2.4 µg/m³, 0.5× usual Green Bay, 11 May: 2.6 µg/m³, 0.5× usual Green Bay, 12 May: 4.7 µg/m³, 0.9× usual Green Bay, 13 May: 28.1 µg/m³, 5.6× usual Green Bay, 14 May: 1.5 µg/m³, 0.3× usual Green Bay, 15 May: 3.2 µg/m³, 0.6× usual Green Bay, 16 May: 9.1 µg/m³, 1.8× usual Green Bay, 17 May: 6.7 µg/m³, 1.3× usual Waterloo Waterloo, 9 May: 4.9 µg/m³, 0.6× usual Waterloo, 10 May: 4.9 µg/m³, 0.6× usual Waterloo, 11 May: 8.1 µg/m³, 0.9× usual Waterloo, 12 May: 7.3 µg/m³, 0.8× usual Waterloo, 13 May: 25.4 µg/m³, 3.0× usual Waterloo, 14 May: 21.2 µg/m³, 2.5× usual Waterloo, 15 May: 16.5 µg/m³, 1.9× usual Waterloo, 16 May: 7.8 µg/m³, 0.9× usual Waterloo, 17 May: 10.5 µg/m³, 1.2× usual Topeka Topeka, 9 May: 3.3 µg/m³, 0.5× usual Topeka, 10 May: 4.6 µg/m³, 0.7× usual Topeka, 11 May: 5.8 µg/m³, 0.9× usual Topeka, 12 May: 6.4 µg/m³, 1.0× usual Topeka, 13 May: 9.2 µg/m³, 1.4× usual Topeka, 14 May: 46.3 µg/m³, 7.2× usual Topeka, 15 May: 16.9 µg/m³, 2.6× usual Topeka, 16 May: 9.3 µg/m³, 1.5× usual Topeka, 17 May: 8.1 µg/m³, 1.3× usual Ponca City Ponca City, 9 May: no reading Ponca City, 10 May: 5.4 µg/m³, 0.8× usual Ponca City, 11 May: 7.4 µg/m³, 1.1× usual Ponca City, 12 May: 10.2 µg/m³, 1.5× usual Ponca City, 13 May: 5.1 µg/m³, 0.8× usual Ponca City, 14 May: 35.5 µg/m³, 5.4× usual Ponca City, 15 May: 30.1 µg/m³, 4.6× usual Ponca City, 16 May: 7.3 µg/m³, 1.1× usual Ponca City, 17 May: 11.4 µg/m³, 1.7× usual Derby Derby, 9 May: 4.5 µg/m³, 0.6× usual Derby, 10 May: 7.4 µg/m³, 1.1× usual Derby, 11 May: 8.4 µg/m³, 1.2× usual Derby, 12 May: 5.1 µg/m³, 0.7× usual Derby, 13 May: 3.5 µg/m³, 0.5× usual Derby, 14 May: 31.8 µg/m³, 4.5× usual Derby, 15 May: 21.4 µg/m³, 3.1× usual Derby, 16 May: 3.7 µg/m³, 0.5× usual Derby, 17 May: 5.8 µg/m³, 0.8× usual Omaha Omaha, 9 May: 3.4 µg/m³, 0.5× usual Omaha, 10 May: 4.3 µg/m³, 0.7× usual Omaha, 11 May: 7.7 µg/m³, 1.2× usual Omaha, 12 May: 6.4 µg/m³, 1.0× usual Omaha, 13 May: 16.3 µg/m³, 2.6× usual Omaha, 14 May: 27.9 µg/m³, 4.4× usual Omaha, 15 May: 8.0 µg/m³, 1.3× usual Omaha, 16 May: 7.4 µg/m³, 1.2× usual Omaha, 17 May: 4.5 µg/m³, 0.7× usual Bellevue Bellevue, 9 May: 2.6 µg/m³, 0.5× usual Bellevue, 10 May: no reading Bellevue, 11 May: 4.4 µg/m³, 0.9× usual Bellevue, 12 May: no reading Bellevue, 13 May: 16.8 µg/m³, 3.4× usual Bellevue, 14 May: 27.6 µg/m³, 5.5× usual Bellevue, 15 May: 4.7 µg/m³, 0.9× usual Bellevue, 16 May: 7.0 µg/m³, 1.4× usual Bellevue, 17 May: 4.3 µg/m³, 0.9× usual Kansas City Kansas City, 9 May: 3.1 µg/m³, 0.5× usual Kansas City, 10 May: 4.9 µg/m³, 0.7× usual Kansas City, 11 May: 8.5 µg/m³, 1.3× usual Kansas City, 12 May: 7.5 µg/m³, 1.1× usual Kansas City, 13 May: 6.6 µg/m³, 1.0× usual Kansas City, 14 May: 25.7 µg/m³, 3.8× usual Kansas City, 15 May: 10.2 µg/m³, 1.5× usual Kansas City, 16 May: 8.8 µg/m³, 1.3× usual Kansas City, 17 May: 10.5 µg/m³, 1.6× usual 9 May 10 11 12 13 14 15 16 17 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
Eau Claire Wisconsin, United States 1 13 May 5.1 11× Burnsville Minnesota, United States 1 13 May 5.5 11× Rochester Minnesota, United States 1 13 May 5.9 10× Apple Valley Minnesota, United States 1 13 May 5.4 9.9× Blaine Minnesota, United States 2 13 May 4.8 9.6× Shakopee Minnesota, United States 1 13 May 6.0 9.0× Minneapolis Minnesota, United States 1 13 May 5.8 8.8× Saint Paul Minnesota, United States 2 13 May 5.7 8.6× Saint Michael Minnesota, United States 2 13 May 5.0 8.4× Thunder Bay Ontario, Canada 1 12 May 3.8 8.1× West Fargo North Dakota, United States 1 12 May 6.0 8.0× Duluth Minnesota, United States 1 12 May 4.0 7.4× Saint Cloud Minnesota, United States 2 13 May 5.1 7.3× Superior Wisconsin, United States 1 12 May 4.6 7.2× Topeka Kansas, United States 1 14 May 6.4 7.2× Appleton Wisconsin, United States 1 13 May 4.7 6.8× Green Bay Wisconsin, United States 1 13 May 4.8 5.6× Bellevue Nebraska, United States 1 14 May 4.9 5.5× Ponca City Oklahoma, United States 1 14 May 6.6 5.4× Watertown South Dakota, United States 2 13 May 6.7 5.0× Brookings South Dakota, United States 1 13 May 7.1 4.7× Derby Kansas, United States 1 14 May 7.0 4.5× Omaha Nebraska, United States 1 14 May 6.3 4.4× Kansas City Kansas, United States 1 14 May 6.7 3.8× Waterloo Iowa, United States 1 13 May 8.6 3.0×
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 40 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 Northern United States, May 2024 25 Bars: cities reached; colour: the level of the episode's highest daily reading. All 142 .
Use this page SmogRank, Northern United States, May 2024: 25 cities with PM2.5 at twice their usual or more, 12 to 14 May 2024, smogrank.com/episodes/2024-05-northern-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.
