SmogRank / Episodes / United States
North-eastern United States, March 2026
For 2 days, from 4 to 5 March 2026, 23 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Brookfield, Illinois, United States: 32.4 µg/m³ on 4 March, about 4.3× its usual 7.5.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 23 in 1 country
Days 2 4 to 5 March 2026
Worst day 4 March 17 cities counted
Furthest above usual 4.8× Clinton
Day by day
Play 4 March 17 cities at twice their usual or more
Madison Elgin Cary Wheaton Waukesha Peoria Brookfield Des Plaines Zion Northbrook Park Ridge Niles South Milwaukee Milwaukee Oak Lawn Bloomington Cedar Rapids East Chicago Appleton Decatur Champaign Michigan City Green Bay Waterloo South Bend Rochester Holland Elkhart Jenison Wyoming Grand Rapids Kalamazoo Ankeny Des Moines Anderson Fort Wayne Muncie Fort Dodge Mankato Lansing Lima Blue Island Evergreen Park Evanston Skokie Dolton Muscatine Naperville Elmwood Park Joliet Aurora Chicago Franklin Park Iowa City Bridgeview Rockford Moline Calumet City Davenport Brookfield Middleton Oconomowoc Hammond Clinton 1 Mar 2 3 4 5 6 7 8 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
Brookfield Brookfield, 1 March: 2.5 µg/m³ Brookfield, 2 March: 9.5 µg/m³ Brookfield, 3 March: 21.5 µg/m³ Brookfield, 4 March: 32.4 µg/m³, 4.3× its usual 7.5 Brookfield, 5 March: 28.2 µg/m³, 3.7× its usual 7.7 Brookfield, 6 March: 18.5 µg/m³ Brookfield, 7 March: 4.9 µg/m³ Brookfield, 8 March: 5.5 µg/m³ Bridgeview Bridgeview, 1 March: 2.3 µg/m³ Bridgeview, 2 March: 14.4 µg/m³ Bridgeview, 3 March: 20.7 µg/m³ Bridgeview, 4 March: 32.0 µg/m³, 4.0× its usual 8.0 Bridgeview, 5 March: 25.0 µg/m³, 2.6× its usual 9.8 Bridgeview, 6 March: 14.8 µg/m³ Bridgeview, 7 March: 4.3 µg/m³ Bridgeview, 8 March: 5.0 µg/m³ Hammond Hammond, 1 March: 3.0 µg/m³ Hammond, 2 March: 6.4 µg/m³ Hammond, 3 March: 17.4 µg/m³ Hammond, 4 March: 30.2 µg/m³, 4.7× its usual 6.4 Hammond, 5 March: 26.6 µg/m³, 3.9× its usual 6.8 Hammond, 6 March: 12.8 µg/m³ Hammond, 7 March: 4.3 µg/m³ Hammond, 8 March: 4.4 µg/m³ Calumet City Calumet City, 1 March: 3.0 µg/m³ Calumet City, 2 March: 6.5 µg/m³ Calumet City, 3 March: 16.9 µg/m³ Calumet City, 4 March: 28.6 µg/m³, 4.1× its usual 7.0 Calumet City, 5 March: 27.9 µg/m³, 3.9× its usual 7.2 Calumet City, 6 March: 14.0 µg/m³ Calumet City, 7 March: 4.7 µg/m³ Calumet City, 8 March: 4.4 µg/m³ Franklin Park Franklin Park, 1 March: 2.5 µg/m³ Franklin Park, 2 March: 7.2 µg/m³ Franklin Park, 3 March: 20.3 µg/m³ Franklin Park, 4 March: 28.2 µg/m³, 3.9× its usual 7.2 Franklin Park, 5 March: 20.8 µg/m³ Franklin Park, 6 March: 14.0 µg/m³ Franklin Park, 7 March: 4.6 µg/m³ Franklin Park, 8 March: 5.5 µg/m³ Skokie Skokie, 1 March: 4.5 µg/m³ Skokie, 2 March: 7.6 µg/m³ Skokie, 3 March: 18.8 µg/m³ Skokie, 4 March: 28.2 µg/m³, 2.6× its usual 10.9 Skokie, 5 March: no reading Skokie, 6 March: 14.8 µg/m³ Skokie, 7 March: 5.8 µg/m³ Skokie, 8 March: 7.7 µg/m³ Oconomowoc Oconomowoc, 1 March: 3.4 µg/m³ Oconomowoc, 2 March: 4.4 µg/m³ Oconomowoc, 3 March: 15.1 µg/m³ Oconomowoc, 4 March: 28.0 µg/m³, 4.7× its usual 6.0 Oconomowoc, 5 March: 24.6 µg/m³ Oconomowoc, 6 March: 11.5 µg/m³ Oconomowoc, 7 March: 4.2 µg/m³ Oconomowoc, 8 March: 6.3 µg/m³ Evergreen Park Evergreen Park, 1 March: 4.2 µg/m³ Evergreen Park, 2 March: 8.4 µg/m³ Evergreen Park, 3 March: 22.1 µg/m³ Evergreen Park, 4 March: 27.5 µg/m³, 2.5× its usual 10.8 Evergreen Park, 5 March: no reading Evergreen Park, 6 March: 15.0 µg/m³ Evergreen Park, 7 March: 5.6 µg/m³ Evergreen Park, 8 March: 7.1 µg/m³ Chicago Chicago, 1 March: 2.4 µg/m³ Chicago, 2 March: 7.4 µg/m³ Chicago, 3 March: 18.5 µg/m³ Chicago, 4 March: 27.4 µg/m³, 3.9× its usual 7.0 Chicago, 5 March: 20.9 µg/m³ Chicago, 6 March: 14.0 µg/m³ Chicago, 7 March: 4.8 µg/m³ Chicago, 8 March: 5.6 µg/m³ Elmwood Park Elmwood Park, 1 March: 2.3 µg/m³ Elmwood Park, 2 March: 6.4 µg/m³ Elmwood Park, 3 March: 18.8 µg/m³ Elmwood Park, 4 March: 27.3 µg/m³, 3.6× its usual 7.6 Elmwood Park, 5 March: 17.9 µg/m³ Elmwood Park, 6 March: 11.3 µg/m³ Elmwood Park, 7 March: 4.6 µg/m³ Elmwood Park, 8 March: 5.5 µg/m³ Blue Island Blue Island, 1 March: 4.2 µg/m³ Blue Island, 2 March: 8.2 µg/m³ Blue Island, 3 March: 20.7 µg/m³ Blue Island, 4 March: 26.9 µg/m³, 2.4× its usual 11.2 Blue Island, 5 March: no reading Blue Island, 6 March: 14.8 µg/m³ Blue Island, 7 March: 5.7 µg/m³ Blue Island, 8 March: 7.1 µg/m³ Joliet Joliet, 1 March: 2.5 µg/m³ Joliet, 2 March: 9.0 µg/m³ Joliet, 3 March: 17.9 µg/m³ Joliet, 4 March: 26.8 µg/m³, 3.8× its usual 7.0 Joliet, 5 March: 20.7 µg/m³ Joliet, 6 March: 10.8 µg/m³ Joliet, 7 March: 4.2 µg/m³ Joliet, 8 March: 4.6 µg/m³ Dolton Dolton, 1 March: 2.4 µg/m³ Dolton, 2 March: 7.1 µg/m³ Dolton, 3 March: 20.1 µg/m³ Dolton, 4 March: 26.8 µg/m³, 3.2× its usual 8.4 Dolton, 5 March: 18.5 µg/m³ Dolton, 6 March: 11.5 µg/m³ Dolton, 7 March: 5.6 µg/m³ Dolton, 8 March: 5.9 µg/m³ Aurora Aurora, 1 March: 2.9 µg/m³ Aurora, 2 March: 7.2 µg/m³ Aurora, 3 March: 16.3 µg/m³ Aurora, 4 March: 26.0 µg/m³, 3.9× its usual 6.6 Aurora, 5 March: 24.3 µg/m³ Aurora, 6 March: 11.9 µg/m³ Aurora, 7 March: 3.9 µg/m³ Aurora, 8 March: 5.0 µg/m³ Muscatine Muscatine, 1 March: no reading Muscatine, 2 March: 8.3 µg/m³ Muscatine, 3 March: 15.3 µg/m³ Muscatine, 4 March: 25.8 µg/m³, 3.3× its usual 7.8 Muscatine, 5 March: 20.9 µg/m³ Muscatine, 6 March: 7.9 µg/m³ Muscatine, 7 March: 5.2 µg/m³ Muscatine, 8 March: 6.1 µg/m³ Naperville Naperville, 1 March: 3.1 µg/m³ Naperville, 2 March: 8.0 µg/m³ Naperville, 3 March: 16.2 µg/m³ Naperville, 4 March: 25.7 µg/m³, 3.6× its usual 7.2 Naperville, 5 March: 22.7 µg/m³ Naperville, 6 March: 12.0 µg/m³ Naperville, 7 March: 3.8 µg/m³ Naperville, 8 March: 4.7 µg/m³ Evanston Evanston, 1 March: 4.3 µg/m³ Evanston, 2 March: 7.5 µg/m³ Evanston, 3 March: 17.7 µg/m³ Evanston, 4 March: 25.1 µg/m³, 2.6× its usual 9.6 Evanston, 5 March: 21.9 µg/m³ Evanston, 6 March: 14.9 µg/m³ Evanston, 7 March: 5.6 µg/m³ Evanston, 8 March: 7.7 µg/m³ Clinton Clinton, 1 March: 4.4 µg/m³ Clinton, 2 March: 6.6 µg/m³ Clinton, 3 March: 21.8 µg/m³ Clinton, 4 March: 19.5 µg/m³ Clinton, 5 March: 31.5 µg/m³, 4.8× its usual 6.6 Clinton, 6 March: 7.5 µg/m³ Clinton, 7 March: 4.4 µg/m³ Clinton, 8 March: 5.5 µg/m³ Middleton Middleton, 1 March: 0.6 µg/m³ Middleton, 2 March: 2.1 µg/m³ Middleton, 3 March: 9.8 µg/m³ Middleton, 4 March: 23.2 µg/m³ Middleton, 5 March: 27.6 µg/m³, 4.4× its usual 6.3 Middleton, 6 March: 8.7 µg/m³ Middleton, 7 March: 0.3 µg/m³ Middleton, 8 March: 1.6 µg/m³ Iowa City Iowa City, 1 March: 4.8 µg/m³ Iowa City, 2 March: 7.6 µg/m³ Iowa City, 3 March: 15.3 µg/m³ Iowa City, 4 March: 23.9 µg/m³ Iowa City, 5 March: 27.1 µg/m³, 4.0× its usual 6.7 Iowa City, 6 March: 8.5 µg/m³ Iowa City, 7 March: 5.5 µg/m³ Iowa City, 8 March: 7.0 µg/m³ Davenport Davenport, 1 March: 4.2 µg/m³ Davenport, 2 March: 5.3 µg/m³ Davenport, 3 March: 16.5 µg/m³ Davenport, 4 March: 24.5 µg/m³ Davenport, 5 March: 27.0 µg/m³, 4.2× its usual 6.4 Davenport, 6 March: 6.5 µg/m³ Davenport, 7 March: 4.0 µg/m³ Davenport, 8 March: 5.0 µg/m³ Moline Moline, 1 March: 4.5 µg/m³ Moline, 2 March: 5.5 µg/m³ Moline, 3 March: 18.4 µg/m³ Moline, 4 March: 23.8 µg/m³ Moline, 5 March: 26.0 µg/m³, 4.1× its usual 6.3 Moline, 6 March: 6.3 µg/m³ Moline, 7 March: 4.2 µg/m³ Moline, 8 March: 5.2 µg/m³ Rockford Rockford, 1 March: 4.2 µg/m³ Rockford, 2 March: 8.4 µg/m³ Rockford, 3 March: 17.3 µg/m³ Rockford, 4 March: 19.4 µg/m³ Rockford, 5 March: 25.7 µg/m³, 4.1× its usual 6.2 Rockford, 6 March: 10.1 µg/m³ Rockford, 7 March: 3.8 µg/m³ Rockford, 8 March: 5.4 µg/m³ 1 Mar 2 3 4 5 6 7 8 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
Clinton Iowa, United States 1 5 March 6.6 4.8× Hammond Indiana, United States 2 4 March 6.4 4.7× Oconomowoc Wisconsin, United States 1 4 March 6.0 4.7× Middleton Wisconsin, United States 1 5 March 6.3 4.4× Brookfield Illinois, United States 2 4 March 7.5 4.3× Davenport Iowa, United States 1 5 March 6.4 4.2× Calumet City Illinois, United States 2 4 March 7.0 4.1× Moline Illinois, United States 1 5 March 6.3 4.1× Rockford Illinois, United States 1 5 March 6.2 4.1× Bridgeview Illinois, United States 2 4 March 8.0 4.0× Iowa City Iowa, United States 1 5 March 6.7 4.0× Franklin Park Illinois, United States 1 4 March 7.2 3.9× Chicago Illinois, United States 1 4 March 7.0 3.9× Aurora Illinois, United States 1 4 March 6.6 3.9× Joliet Illinois, United States 1 4 March 7.0 3.8× Elmwood Park Illinois, United States 1 4 March 7.6 3.6× Naperville Illinois, United States 1 4 March 7.2 3.6× Muscatine Iowa, United States 1 4 March 7.8 3.3× Dolton Illinois, United States 1 4 March 8.4 3.2× Skokie Illinois, United States 1 4 March 10.9 2.6× Evanston Illinois, United States 1 4 March 9.6 2.6× Evergreen Park Illinois, United States 1 4 March 10.8 2.5× Blue Island Illinois, United States 1 4 March 11.2 2.4×
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 the United States
Number 45 of 130 episodes in the United States since our records began, by cities reached.
Eastern United States and Canada, 25 June to 2 July 2023 280 North-eastern United States and Canada, July 2026 264 Eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, 30 July to 9 August 2025 241 Eastern United States and Canada, July 2023 240 North-eastern United States and Canada, 3 to 9 June 2025 196 Eastern United States and Canada, 14 to 19 June 2023 161 North-eastern United States and Canada, 12 to 16 July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, 10 to 14 June 2025 104 North-western United States and Canada, 4 to 11 August 2026 99 North-eastern United States and Canada, 14 to 19 February 2026 96 North-eastern United States, March 2026 23 Bars: cities reached; colour: the level of the episode's highest daily reading. All 130 .
Use this page SmogRank, North-eastern United States, March 2026: 23 cities with PM2.5 at twice their usual or more, 4 to 5 March 2026, smogrank.com/episodes/2026-03-north-eastern-united-states (accessed 4 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.
