SmogRank / Episodes / United States
Northern United States, May 2023
For 2 days, from 18 to 19 May 2023, 24 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was West Fargo, North Dakota, United States: 99.0 µg/m³ on 18 May, about 17× its usual 6.0.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 24 in 1 country
Days 2 18 to 19 May 2023
Worst day 18 May 17 cities counted
Furthest above usual 17× Bismarck
Day by day
Play 18 May 17 cities at twice their usual or more
Ankeny Des Moines Waterloo Sioux Falls Eau Claire La Crosse Bellevue Superior Duluth Muscatine Davenport Moline Clinton Rockford Peoria Appleton Bloomington Green Bay Naperville South Milwaukee Zion Joliet Franklin Park Oak Lawn Chicago Calumet City Hammond East Chicago Gary Portage Lafayette Milwaukee Waukesha Cary Des Plaines Iowa City Rochester Northbrook Blaine Madison Omaha Saint Paul Lincoln Minneapolis Saint Michael Burnsville Brookings Apple Valley Saint Cloud Grand Island Shakopee Watertown Bismarck West Fargo Aberdeen 15 May 16 17 18 19 20 21 22 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, 15 May: 11.0 µg/m³, 1.8× usual West Fargo, 16 May: 27.1 µg/m³, 4.5× usual West Fargo, 17 May: 40.7 µg/m³, 6.8× usual West Fargo, 18 May: 99.0 µg/m³, 17× usual West Fargo, 19 May: 4.3 µg/m³, 0.7× usual West Fargo, 20 May: 10.9 µg/m³, 1.8× usual West Fargo, 21 May: 16.3 µg/m³, 2.7× usual West Fargo, 22 May: 20.6 µg/m³, 3.4× usual Bismarck Bismarck, 15 May: 8.0 µg/m³, 1.6× usual Bismarck, 16 May: 7.2 µg/m³, 1.4× usual Bismarck, 17 May: 190.0 µg/m³, 38× usual Bismarck, 18 May: 65.0 µg/m³, 13× usual Bismarck, 19 May: 6.4 µg/m³, 1.3× usual Bismarck, 20 May: 11.5 µg/m³, 2.3× usual Bismarck, 21 May: 22.3 µg/m³, 4.5× usual Bismarck, 22 May: 16.9 µg/m³, 3.4× usual Aberdeen Aberdeen, 15 May: 3.4 µg/m³, 0.7× usual Aberdeen, 16 May: 4.6 µg/m³, 0.9× usual Aberdeen, 17 May: 46.0 µg/m³, 9.2× usual Aberdeen, 18 May: 82.8 µg/m³, 17× usual Aberdeen, 19 May: 3.3 µg/m³, 0.7× usual Aberdeen, 20 May: 5.0 µg/m³, 1.0× usual Aberdeen, 21 May: 7.9 µg/m³, 1.6× usual Aberdeen, 22 May: 16.2 µg/m³, 3.2× usual Watertown Watertown, 15 May: 7.1 µg/m³, 1.1× usual Watertown, 16 May: 10.7 µg/m³, 1.6× usual Watertown, 17 May: 11.2 µg/m³, 1.7× usual Watertown, 18 May: 82.8 µg/m³, 13× usual Watertown, 19 May: 6.0 µg/m³, 0.9× usual Watertown, 20 May: 12.7 µg/m³, 1.9× usual Watertown, 21 May: 22.2 µg/m³, 3.4× usual Watertown, 22 May: 18.3 µg/m³, 2.8× usual Brookings Brookings, 15 May: 4.2 µg/m³, 0.6× usual Brookings, 16 May: 6.4 µg/m³, 0.9× usual Brookings, 17 May: 7.6 µg/m³, 1.1× usual Brookings, 18 May: 63.8 µg/m³, 9.1× usual Brookings, 19 May: 2.9 µg/m³, 0.4× usual Brookings, 20 May: 8.6 µg/m³, 1.2× usual Brookings, 21 May: 16.8 µg/m³, 2.4× usual Brookings, 22 May: 9.5 µg/m³, 1.4× usual Shakopee Shakopee, 15 May: 7.0 µg/m³, 1.2× usual Shakopee, 16 May: 11.1 µg/m³, 1.8× usual Shakopee, 17 May: 9.1 µg/m³, 1.5× usual Shakopee, 18 May: 59.0 µg/m³, 9.8× usual Shakopee, 19 May: 8.0 µg/m³, 1.3× usual Shakopee, 20 May: 11.2 µg/m³, 1.9× usual Shakopee, 21 May: 23.0 µg/m³, 3.8× usual Shakopee, 22 May: 18.6 µg/m³, 3.1× usual Burnsville Burnsville, 15 May: 8.2 µg/m³, 1.5× usual Burnsville, 16 May: 11.7 µg/m³, 2.1× usual Burnsville, 17 May: 8.7 µg/m³, 1.6× usual Burnsville, 18 May: 50.1 µg/m³, 8.9× usual Burnsville, 19 May: 10.0 µg/m³, 1.8× usual Burnsville, 20 May: 12.3 µg/m³, 2.2× usual Burnsville, 21 May: 26.1 µg/m³, 4.7× usual Burnsville, 22 May: 20.5 µg/m³, 3.7× usual Apple Valley Apple Valley, 15 May: 7.6 µg/m³, 1.4× usual Apple Valley, 16 May: 10.8 µg/m³, 2.0× usual Apple Valley, 17 May: 8.4 µg/m³, 1.6× usual Apple Valley, 18 May: 49.9 µg/m³, 9.4× usual Apple Valley, 19 May: 9.0 µg/m³, 1.7× usual Apple Valley, 20 May: 10.9 µg/m³, 2.1× usual Apple Valley, 21 May: 17.9 µg/m³, 3.4× usual Apple Valley, 22 May: 18.7 µg/m³, 3.5× usual Grand Island Grand Island, 15 May: 4.6 µg/m³, 0.9× usual Grand Island, 16 May: 5.1 µg/m³, 1.0× usual Grand Island, 17 May: 5.0 µg/m³, 1.0× usual Grand Island, 18 May: 49.2 µg/m³, 9.8× usual Grand Island, 19 May: 24.8 µg/m³, 5.0× usual Grand Island, 20 May: no reading Grand Island, 21 May: 11.5 µg/m³, 2.3× usual Grand Island, 22 May: 10.0 µg/m³, 2.0× usual Saint Cloud Saint Cloud, 15 May: 7.2 µg/m³, 1.4× usual Saint Cloud, 16 May: 14.1 µg/m³, 2.8× usual Saint Cloud, 17 May: 7.7 µg/m³, 1.5× usual Saint Cloud, 18 May: 48.4 µg/m³, 9.7× usual Saint Cloud, 19 May: 6.9 µg/m³, 1.4× usual Saint Cloud, 20 May: 9.0 µg/m³, 1.8× usual Saint Cloud, 21 May: 18.4 µg/m³, 3.7× usual Saint Cloud, 22 May: 16.5 µg/m³, 3.3× usual Saint Michael Saint Michael, 15 May: 7.0 µg/m³, 1.4× usual Saint Michael, 16 May: 12.1 µg/m³, 2.4× usual Saint Michael, 17 May: 7.9 µg/m³, 1.6× usual Saint Michael, 18 May: 40.7 µg/m³, 8.1× usual Saint Michael, 19 May: 6.6 µg/m³, 1.3× usual Saint Michael, 20 May: 9.5 µg/m³, 1.9× usual Saint Michael, 21 May: 16.7 µg/m³, 3.3× usual Saint Michael, 22 May: 17.5 µg/m³, 3.5× usual Minneapolis Minneapolis, 15 May: 8.8 µg/m³, 1.6× usual Minneapolis, 16 May: 11.6 µg/m³, 2.1× usual Minneapolis, 17 May: 8.0 µg/m³, 1.4× usual Minneapolis, 18 May: 38.5 µg/m³, 6.9× usual Minneapolis, 19 May: 8.4 µg/m³, 1.5× usual Minneapolis, 20 May: 9.8 µg/m³, 1.8× usual Minneapolis, 21 May: 24.9 µg/m³, 4.4× usual Minneapolis, 22 May: 21.2 µg/m³, 3.8× usual Saint Paul Saint Paul, 15 May: 10.1 µg/m³, 1.7× usual Saint Paul, 16 May: 11.4 µg/m³, 1.9× usual Saint Paul, 17 May: 6.5 µg/m³, 1.1× usual Saint Paul, 18 May: 32.8 µg/m³, 5.6× usual Saint Paul, 19 May: 11.0 µg/m³, 1.9× usual Saint Paul, 20 May: 14.1 µg/m³, 2.4× usual Saint Paul, 21 May: 21.4 µg/m³, 3.6× usual Saint Paul, 22 May: 18.2 µg/m³, 3.1× usual Omaha Omaha, 15 May: 7.2 µg/m³, 1.3× usual Omaha, 16 May: 9.5 µg/m³, 1.7× usual Omaha, 17 May: 9.8 µg/m³, 1.7× usual Omaha, 18 May: 31.2 µg/m³, 5.5× usual Omaha, 19 May: 18.1 µg/m³, 3.2× usual Omaha, 20 May: 10.7 µg/m³, 1.9× usual Omaha, 21 May: 12.1 µg/m³, 2.1× usual Omaha, 22 May: 14.5 µg/m³, 2.5× usual Lincoln Lincoln, 15 May: 11.0 µg/m³, 2.2× usual Lincoln, 16 May: 5.8 µg/m³, 1.2× usual Lincoln, 17 May: 8.4 µg/m³, 1.7× usual Lincoln, 18 May: 29.3 µg/m³, 5.9× usual Lincoln, 19 May: 21.2 µg/m³, 4.2× usual Lincoln, 20 May: 7.3 µg/m³, 1.5× usual Lincoln, 21 May: 9.0 µg/m³, 1.8× usual Lincoln, 22 May: 11.4 µg/m³, 2.3× usual Rochester Rochester, 15 May: 8.5 µg/m³, 1.4× usual Rochester, 16 May: 9.8 µg/m³, 1.6× usual Rochester, 17 May: 7.5 µg/m³, 1.2× usual Rochester, 18 May: 28.0 µg/m³, 4.6× usual Rochester, 19 May: 13.3 µg/m³, 2.2× usual Rochester, 20 May: 12.4 µg/m³, 2.0× usual Rochester, 21 May: 17.1 µg/m³, 2.8× usual Rochester, 22 May: 20.7 µg/m³, 3.4× usual Blaine Blaine, 15 May: 5.2 µg/m³, 1.0× usual Blaine, 16 May: 7.1 µg/m³, 1.4× usual Blaine, 17 May: 4.3 µg/m³, 0.9× usual Blaine, 18 May: 25.2 µg/m³, 5.0× usual Blaine, 19 May: 5.0 µg/m³, 1.0× usual Blaine, 20 May: 7.2 µg/m³, 1.4× usual Blaine, 21 May: 17.1 µg/m³, 3.4× usual Blaine, 22 May: 14.3 µg/m³, 2.9× usual Northbrook Northbrook, 15 May: 5.3 µg/m³, 0.9× usual Northbrook, 16 May: 8.3 µg/m³, 1.5× usual Northbrook, 17 May: 3.5 µg/m³, 0.6× usual Northbrook, 18 May: 6.9 µg/m³, 1.2× usual Northbrook, 19 May: 27.6 µg/m³, 4.9× usual Northbrook, 20 May: 7.0 µg/m³, 1.3× usual Northbrook, 21 May: 7.9 µg/m³, 1.4× usual Northbrook, 22 May: 7.9 µg/m³, 1.4× usual Iowa City Iowa City, 15 May: 7.3 µg/m³, 1.3× usual Iowa City, 16 May: 9.1 µg/m³, 1.6× usual Iowa City, 17 May: 7.9 µg/m³, 1.4× usual Iowa City, 18 May: 11.0 µg/m³, 1.9× usual Iowa City, 19 May: 26.7 µg/m³, 4.6× usual Iowa City, 20 May: 9.0 µg/m³, 1.6× usual Iowa City, 21 May: 11.5 µg/m³, 2.0× usual Iowa City, 22 May: 16.2 µg/m³, 2.8× usual Des Plaines Des Plaines, 15 May: 5.8 µg/m³, 1.0× usual Des Plaines, 16 May: 8.8 µg/m³, 1.5× usual Des Plaines, 17 May: 3.6 µg/m³, 0.6× usual Des Plaines, 18 May: 7.6 µg/m³, 1.3× usual Des Plaines, 19 May: 26.2 µg/m³, 4.5× usual Des Plaines, 20 May: 8.3 µg/m³, 1.4× usual Des Plaines, 21 May: no reading Des Plaines, 22 May: no reading Cary Cary, 15 May: 6.5 µg/m³, 1.1× usual Cary, 16 May: 9.4 µg/m³, 1.6× usual Cary, 17 May: 3.8 µg/m³, 0.7× usual Cary, 18 May: 7.8 µg/m³, 1.3× usual Cary, 19 May: 25.7 µg/m³, 4.4× usual Cary, 20 May: 7.4 µg/m³, 1.3× usual Cary, 21 May: 7.5 µg/m³, 1.3× usual Cary, 22 May: 9.3 µg/m³, 1.6× usual Madison Madison, 15 May: 6.3 µg/m³, 1.3× usual Madison, 16 May: 8.7 µg/m³, 1.7× usual Madison, 17 May: 5.7 µg/m³, 1.1× usual Madison, 18 May: 8.3 µg/m³, 1.7× usual Madison, 19 May: 25.5 µg/m³, 5.1× usual Madison, 20 May: 5.7 µg/m³, 1.1× usual Madison, 21 May: 8.2 µg/m³, 1.6× usual Madison, 22 May: 10.2 µg/m³, 2.0× usual Milwaukee Milwaukee, 15 May: 6.1 µg/m³, 0.9× usual Milwaukee, 16 May: 8.3 µg/m³, 1.3× usual Milwaukee, 17 May: 4.6 µg/m³, 0.7× usual Milwaukee, 18 May: 9.8 µg/m³, 1.5× usual Milwaukee, 19 May: 25.3 µg/m³, 3.9× usual Milwaukee, 20 May: 8.0 µg/m³, 1.2× usual Milwaukee, 21 May: 9.6 µg/m³, 1.5× usual Milwaukee, 22 May: 11.8 µg/m³, 1.8× usual Waukesha Waukesha, 15 May: 5.6 µg/m³, 0.9× usual Waukesha, 16 May: 8.5 µg/m³, 1.4× usual Waukesha, 17 May: 4.2 µg/m³, 0.7× usual Waukesha, 18 May: 8.7 µg/m³, 1.5× usual Waukesha, 19 May: 25.0 µg/m³, 4.2× usual Waukesha, 20 May: 6.6 µg/m³, 1.1× usual Waukesha, 21 May: 10.0 µg/m³, 1.7× usual Waukesha, 22 May: 10.9 µg/m³, 1.8× usual 15 May 16 17 18 19 20 21 22 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
Bismarck North Dakota, United States 1 17 May 4.7 38× Aberdeen South Dakota, United States 1 18 May 3.8 17× West Fargo North Dakota, United States 1 18 May 6.0 17× Watertown South Dakota, United States 1 18 May 6.6 13× Grand Island Nebraska, United States 1 18 May 5.0 9.8× Shakopee Minnesota, United States 1 18 May 6.0 9.8× Saint Cloud Minnesota, United States 1 18 May 4.8 9.7× Apple Valley Minnesota, United States 1 18 May 5.3 9.4× Brookings South Dakota, United States 1 18 May 7.0 9.1× Burnsville Minnesota, United States 1 18 May 5.6 8.9× Saint Michael Minnesota, United States 1 18 May 5.0 8.1× Minneapolis Minnesota, United States 1 18 May 5.6 6.9× Lincoln Nebraska, United States 1 18 May 4.8 5.9× Saint Paul Minnesota, United States 1 18 May 5.9 5.6× Omaha Nebraska, United States 1 18 May 5.7 5.5× Madison Wisconsin, United States 1 19 May 5.0 5.1× Blaine Minnesota, United States 1 18 May 4.8 5.0× Northbrook Illinois, United States 1 19 May 5.6 4.9× Iowa City Iowa, United States 1 19 May 5.8 4.6× Rochester Minnesota, United States 1 18 May 6.1 4.6× Des Plaines Illinois, United States 1 19 May 5.8 4.5× Cary Illinois, United States 1 19 May 5.8 4.4× Waukesha Wisconsin, United States 1 19 May 5.9 4.2× Milwaukee Wisconsin, United States 1 19 May 6.5 3.9×
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
Number 17 of 41 episodes in 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 Northern United States, May 2023 24 Bars: cities reached; colour: the level of the episode's highest daily reading. All 41 .
Use this page SmogRank, Northern United States, May 2023: 24 cities with PM2.5 at twice their usual or more, 18 to 19 May 2023, smogrank.com/episodes/2023-05-northern-united-states (accessed 2 October 2026).
Copy citation Download top 10 (PNG)
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.
