SmogRank / Episodes / United States
North-eastern United States and Canada, March 2026
For 2 days, from 4 to 5 March 2026, 40 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Hamilton, Ontario, Canada: 37.6 µg/m³ on 4 March, about 6.3× its usual 6.0. Ended 5 March.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 40 in 2 countries
Days 2 4 to 5 March 2026
Worst day 4 March 34 cities counted
Furthest above usual 6.7× Waterdown
Day by day
Play 4 March 34 cities at twice their usual or more
Beecher Bay City Southfield Royal Oak Ann Arbor Ypsilanti Eastpointe Dearborn Hamtramck New Baltimore Lansing Taylor Detroit Lincoln Park Windsor Port Huron Sarnia Tecumseh Toledo Oregon Chatham Maumee Perrysburg Grand Rapids Wyoming Kalamazoo Jenison Hudsonville St. Thomas Holland Fort Wayne Cleveland Cleveland Heights Shaker Heights Medina Warrensville Heights Elkhart Painesville Manistee Akron South Bend Canton Brantford Guelph Warren Michigan City Youngstown Erie Hermitage East Chicago Parry Sound South Milwaukee Winthrop Harbor Zion Milwaukee Northbrook Niles Greendale St. Catharines Park Ridge Oak Lawn Des Plaines Brookfield Green Bay Waukesha Wheaton Warren Cary Buffalo Elgin Appleton Braidwood Peterborough Madison Rochester Baraboo State College Belleville Tomah Kingston Syracuse Altoona Eau Claire Cedar Rapids Scranton Ottawa Gatineau Utica Waterloo Rochester Cornwall Randolph Redford Blue Island Evanston Evergreen Park Skokie Dolton Muscatine Elmwood Park Columbia City Naperville Lincolnwood Joliet Warrenville Aurora Chicago Franklin Park Iowa City Bridgeview Rockford Moline Calumet City Davenport Brookfield Middleton Oconomowoc Hammond Clinton Brampton Toronto Barrie Nepean Milton Newmarket Kitchener Mississauga Oakville London Alliston Hamilton Waterdown 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
Hamilton Hamilton, 1 March: 2.5 µg/m³ Hamilton, 2 March: 5.3 µg/m³ Hamilton, 3 March: 14.0 µg/m³ Hamilton, 4 March: 37.6 µg/m³, 6.3× its usual 6.0 Hamilton, 5 March: 18.5 µg/m³ Hamilton, 6 March: 8.7 µg/m³ Hamilton, 7 March: 5.9 µg/m³ Hamilton, 8 March: 2.9 µg/m³ Waterdown Waterdown, 1 March: 2.8 µg/m³ Waterdown, 2 March: 4.4 µg/m³ Waterdown, 3 March: 13.0 µg/m³ Waterdown, 4 March: 36.4 µg/m³, 6.7× its usual 5.4 Waterdown, 5 March: 16.4 µg/m³ Waterdown, 6 March: 7.8 µg/m³ Waterdown, 7 March: 6.4 µg/m³ Waterdown, 8 March: 2.8 µg/m³ 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 London London, 1 March: 2.5 µg/m³ London, 2 March: 4.8 µg/m³ London, 3 March: 15.4 µg/m³ London, 4 March: 30.6 µg/m³, 5.6× its usual 5.5 London, 5 March: 16.7 µg/m³ London, 6 March: 12.5 µg/m³ London, 7 March: 5.6 µg/m³ London, 8 March: 2.7 µg/m³ Toronto Toronto, 1 March: 3.3 µg/m³ Toronto, 2 March: 5.7 µg/m³ Toronto, 3 March: 15.1 µg/m³ Toronto, 4 March: 30.6 µg/m³, 5.0× its usual 6.1 Toronto, 5 March: 15.3 µg/m³ Toronto, 6 March: 9.6 µg/m³ Toronto, 7 March: 10.8 µg/m³ Toronto, 8 March: 3.7 µg/m³ Oakville Oakville, 1 March: 2.8 µg/m³ Oakville, 2 March: 4.4 µg/m³ Oakville, 3 March: 13.9 µg/m³ Oakville, 4 March: 30.4 µg/m³, 5.6× its usual 5.4 Oakville, 5 March: 17.7 µg/m³ Oakville, 6 March: 7.5 µg/m³ Oakville, 7 March: 6.9 µg/m³ Oakville, 8 March: 2.9 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, 4.0× its usual 6.6 Hammond, 6 March: 12.8 µg/m³ Hammond, 7 March: 4.3 µg/m³ Hammond, 8 March: 4.4 µg/m³ Milton Milton, 1 March: 2.8 µg/m³ Milton, 2 March: 5.6 µg/m³ Milton, 3 March: 16.7 µg/m³ Milton, 4 March: 29.3 µg/m³, 5.3× its usual 5.5 Milton, 5 March: 16.7 µg/m³ Milton, 6 March: 8.1 µg/m³ Milton, 7 March: 6.4 µg/m³ Milton, 8 March: 3.9 µg/m³ Kitchener Kitchener, 1 March: 2.4 µg/m³ Kitchener, 2 March: 5.2 µg/m³ Kitchener, 3 March: 11.6 µg/m³ Kitchener, 4 March: 28.7 µg/m³, 5.4× its usual 5.3 Kitchener, 5 March: 16.6 µg/m³ Kitchener, 6 March: 9.1 µg/m³ Kitchener, 7 March: 5.8 µg/m³ Kitchener, 8 March: 3.1 µg/m³ Elmwood Park Elmwood Park, 1 March: 4.0 µg/m³ Elmwood Park, 2 March: 8.4 µg/m³ Elmwood Park, 3 March: 20.6 µg/m³ Elmwood Park, 4 March: 28.7 µg/m³, 3.3× its usual 8.6 Elmwood Park, 5 March: 25.7 µg/m³, 2.9× its usual 9.0 Elmwood Park, 6 March: 15.7 µg/m³ Elmwood Park, 7 March: 5.7 µg/m³ Elmwood Park, 8 March: 7.5 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 7.1 Calumet City, 6 March: 14.0 µg/m³ Calumet City, 7 March: 4.7 µg/m³ Calumet City, 8 March: 4.4 µg/m³ Alliston Alliston, 1 March: 2.3 µg/m³ Alliston, 2 March: 4.5 µg/m³ Alliston, 3 March: 12.3 µg/m³ Alliston, 4 March: 28.4 µg/m³, 5.7× its usual 4.5 Alliston, 5 March: 12.2 µg/m³ Alliston, 6 March: 8.3 µg/m³ Alliston, 7 March: 5.5 µg/m³ Alliston, 8 March: 3.0 µg/m³ Newmarket Newmarket, 1 March: no reading Newmarket, 2 March: no reading Newmarket, 3 March: 13.9 µg/m³ Newmarket, 4 March: 28.4 µg/m³, 5.4× its usual 5.3 Newmarket, 5 March: 10.9 µg/m³ Newmarket, 6 March: 8.5 µg/m³ Newmarket, 7 March: 7.5 µg/m³ Newmarket, 8 March: 3.3 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 Mississauga Mississauga, 1 March: 2.8 µg/m³ Mississauga, 2 March: 4.4 µg/m³ Mississauga, 3 March: 13.6 µg/m³ Mississauga, 4 March: 28.1 µg/m³, 5.6× its usual 5.0 Mississauga, 5 March: 17.1 µg/m³ Mississauga, 6 March: 7.6 µg/m³ Mississauga, 7 March: 9.0 µg/m³ Mississauga, 8 March: 2.9 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 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 Lincolnwood Lincolnwood, 1 March: 2.3 µg/m³ Lincolnwood, 2 March: 6.4 µg/m³ Lincolnwood, 3 March: 18.8 µg/m³ Lincolnwood, 4 March: 27.3 µg/m³, 3.6× its usual 7.6 Lincolnwood, 5 March: 17.9 µg/m³ Lincolnwood, 6 March: 11.3 µg/m³ Lincolnwood, 7 March: 4.6 µg/m³ Lincolnwood, 8 March: 5.5 µg/m³ Nepean Nepean, 1 March: 1.4 µg/m³ Nepean, 2 March: 2.6 µg/m³ Nepean, 3 March: 19.3 µg/m³ Nepean, 4 March: 27.2 µg/m³, 5.1× its usual 5.3 Nepean, 5 March: 8.9 µg/m³ Nepean, 6 March: 11.6 µg/m³ Nepean, 7 March: 20.4 µg/m³ Nepean, 8 March: 4.5 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: 27.2 µg/m³, 2.5× its usual 11.1 Evergreen Park, 5 March: no reading Evergreen Park, 6 March: 14.9 µg/m³ Evergreen Park, 7 March: 5.6 µg/m³ Evergreen Park, 8 March: 7.2 µg/m³ Redford Redford, 1 March: 7.2 µg/m³ Redford, 2 March: 10.4 µg/m³ Redford, 3 March: 22.2 µg/m³ Redford, 4 March: 27.0 µg/m³, 2.3× its usual 11.7 Redford, 5 March: 19.7 µg/m³ Redford, 6 March: 25.7 µg/m³ Redford, 7 March: 9.9 µg/m³ Redford, 8 March: 8.6 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 Barrie Barrie, 1 March: 3.5 µg/m³ Barrie, 2 March: 6.3 µg/m³ Barrie, 3 March: 9.9 µg/m³ Barrie, 4 March: 26.5 µg/m³, 5.1× its usual 5.2 Barrie, 5 March: 13.2 µg/m³ Barrie, 6 March: 7.7 µg/m³ Barrie, 7 March: 6.3 µg/m³ Barrie, 8 March: 3.1 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 Warrenville Warrenville, 1 March: 2.9 µg/m³ Warrenville, 2 March: 7.2 µg/m³ Warrenville, 3 March: 16.3 µg/m³ Warrenville, 4 March: 26.0 µg/m³, 3.9× its usual 6.6 Warrenville, 5 March: 24.3 µg/m³ Warrenville, 6 March: 11.9 µg/m³ Warrenville, 7 March: 3.9 µg/m³ Warrenville, 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 7.1 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 Columbia City Columbia City, 1 March: 5.2 µg/m³ Columbia City, 2 March: 5.3 µg/m³ Columbia City, 3 March: 20.3 µg/m³ Columbia City, 4 March: 25.7 µg/m³, 3.6× its usual 7.1 Columbia City, 5 March: 10.8 µg/m³ Columbia City, 6 March: 11.4 µg/m³ Columbia City, 7 March: 5.0 µg/m³ Columbia City, 8 March: 4.9 µg/m³ Brampton Brampton, 1 March: 2.5 µg/m³ Brampton, 2 March: 4.5 µg/m³ Brampton, 3 March: 14.0 µg/m³ Brampton, 4 March: 25.1 µg/m³, 5.0× its usual 4.7 Brampton, 5 March: 14.7 µg/m³ Brampton, 6 March: 11.1 µg/m³ Brampton, 7 March: 8.7 µg/m³ Brampton, 8 March: 2.9 µg/m³ Evanston Evanston, 1 March: 4.3 µg/m³ Evanston, 2 March: 7.5 µg/m³ Evanston, 3 March: 17.5 µg/m³ Evanston, 4 March: 25.1 µg/m³, 2.5× its usual 9.9 Evanston, 5 March: 18.1 µg/m³ Evanston, 6 March: 14.6 µg/m³ Evanston, 7 March: 5.8 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 6.5 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
Waterdown Ontario, Canada 1 4 March 5.4 6.7× Hamilton Ontario, Canada 1 4 March 6.0 6.3× Alliston Ontario, Canada 1 4 March 4.5 5.7× London Ontario, Canada 1 4 March 5.5 5.6× Oakville Ontario, Canada 1 4 March 5.4 5.6× Mississauga Ontario, Canada 1 4 March 5.0 5.6× Kitchener Ontario, Canada 1 4 March 5.3 5.4× Newmarket Ontario, Canada 1 4 March 5.3 5.4× Milton Ontario, Canada 1 4 March 5.5 5.3× Nepean Ontario, Canada 1 4 March 5.3 5.1× Barrie Ontario, Canada 1 4 March 5.2 5.1× Toronto Ontario, Canada 1 4 March 6.1 5.0× Brampton Ontario, Canada 1 4 March 4.7 5.0× Clinton Iowa, United States 1 5 March 6.5 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× Warrenville Illinois, United States 1 4 March 6.6 3.9× Joliet Illinois, United States 1 4 March 7.0 3.8× Lincolnwood Illinois, United States 1 4 March 7.6 3.6× Naperville Illinois, United States 1 4 March 7.1 3.6× Columbia City Indiana, United States 1 4 March 7.1 3.6× Elmwood Park Illinois, United States 2 4 March 8.6 3.3× 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× Evergreen Park Illinois, United States 1 4 March 11.1 2.5× Evanston Illinois, United States 1 4 March 9.9 2.5× Blue Island Illinois, United States 1 4 March 11.2 2.4× Redford Michigan, United States 1 4 March 11.7 2.3×
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 and Canada
Number 34 of 173 episodes in the United States and Canada since our records began, by cities reached.
Eastern United States and Canada, June and July 2023 343 Northern United States and Canada, July 2026 327 United States and Canada, July 2023 322 Eastern United States and Canada, May and June 2023 317 North-eastern United States and Canada, 29 July to 9 August 2025 292 Northern United States and Canada, May and June 2025 247 United States and Canada, June 2023 195 North-western United States and Canada, August 2023 176 North-western United States and Canada, 4 to 22 August 2026 151 Northern United States and Canada, July 2025 139 Northern United States and Canada, June 2025 134 North-western United States and Canada, July and August 2026 118 North-eastern United States and Canada, March 2026 40 Bars: cities reached; colour: the level of the episode's highest daily reading. All 173 .
Use this page SmogRank, North-eastern United States and Canada, March 2026: 40 cities with PM2.5 at twice their usual or more, 4 to 5 March 2026, smogrank.com/episodes/2026-03-north-eastern-united-states-and-canada (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.
