SmogRank / Episodes / Canada
Ontario, Canada, August 2023
For 1 day, on 16 August 2023, 16 cities in Canada had PM2.5 at least twice their usual for the time of year. The worst reading was North Bay, Ontario, Canada: 44.6 µg/m³ on 16 August, about 7.8× its usual 5.7.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 16 in 1 country
Days 1 16 August 2023
Worst day 16 August 16 cities counted
Furthest above usual 7.8× North Bay
Day by day
Play 16 August 16 cities at twice their usual or more
Brooklin St. Catharines Peterborough Kenmore Buffalo Cheektowaga Sarnia Port Huron Chatham Belleville Rochester Windsor Detroit Dearborn Bay City Lincoln Park Redford Flint Taylor Kingston Ypsilanti Sault Ste. Marie Syracuse Lansing Ottawa Hamilton Brantford Toronto Milton London Brampton Waterdown Kitchener St. Thomas Guelph Newmarket Mississauga Barrie Oakville Greater Sudbury North Bay 13 Aug 14 15 16 17 18 19 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
Greater Sudbury Greater Sudbury, 13 August: 7.8 µg/m³, 1.3× usual Greater Sudbury, 14 August: 37.1 µg/m³, 6.2× usual Greater Sudbury, 15 August: 79.5 µg/m³, 13× usual Greater Sudbury, 16 August: 33.4 µg/m³, 5.6× usual Greater Sudbury, 17 August: 11.7 µg/m³, 2.0× usual Greater Sudbury, 18 August: 5.8 µg/m³, 1.0× usual Greater Sudbury, 19 August: 22.0 µg/m³, 3.7× usual North Bay North Bay, 13 August: 6.6 µg/m³, 1.2× usual North Bay, 14 August: 24.9 µg/m³, 4.4× usual North Bay, 15 August: 76.7 µg/m³, 13× usual North Bay, 16 August: 44.6 µg/m³, 7.8× usual North Bay, 17 August: 15.5 µg/m³, 2.7× usual North Bay, 18 August: 6.6 µg/m³, 1.2× usual North Bay, 19 August: 16.8 µg/m³, 2.9× usual Barrie Barrie, 13 August: 3.4 µg/m³, 0.4× usual Barrie, 14 August: 16.5 µg/m³, 2.1× usual Barrie, 15 August: 30.2 µg/m³, 3.8× usual Barrie, 16 August: 38.3 µg/m³, 4.8× usual Barrie, 17 August: 21.8 µg/m³, 2.8× usual Barrie, 18 August: 4.3 µg/m³, 0.5× usual Barrie, 19 August: 20.4 µg/m³, 2.6× usual Oakville Oakville, 13 August: 4.0 µg/m³, 0.5× usual Oakville, 14 August: 9.0 µg/m³, 1.2× usual Oakville, 15 August: 14.6 µg/m³, 1.9× usual Oakville, 16 August: 39.1 µg/m³, 5.0× usual Oakville, 17 August: 21.8 µg/m³, 2.8× usual Oakville, 18 August: 8.4 µg/m³, 1.1× usual Oakville, 19 August: 18.5 µg/m³, 2.4× usual Newmarket Newmarket, 13 August: 3.3 µg/m³, 0.4× usual Newmarket, 14 August: 8.8 µg/m³, 1.1× usual Newmarket, 15 August: 17.5 µg/m³, 2.3× usual Newmarket, 16 August: 36.1 µg/m³, 4.7× usual Newmarket, 17 August: 22.0 µg/m³, 2.9× usual Newmarket, 18 August: 4.7 µg/m³, 0.6× usual Newmarket, 19 August: 18.2 µg/m³, 2.4× usual Milton Milton, 13 August: 3.9 µg/m³, 0.5× usual Milton, 14 August: 8.9 µg/m³, 1.1× usual Milton, 15 August: 15.5 µg/m³, 1.9× usual Milton, 16 August: 33.7 µg/m³, 4.1× usual Milton, 17 August: 20.3 µg/m³, 2.4× usual Milton, 18 August: 8.1 µg/m³, 1.0× usual Milton, 19 August: 17.7 µg/m³, 2.1× usual Mississauga Mississauga, 13 August: 3.5 µg/m³, 0.5× usual Mississauga, 14 August: 8.0 µg/m³, 1.2× usual Mississauga, 15 August: 12.8 µg/m³, 1.9× usual Mississauga, 16 August: 32.8 µg/m³, 4.8× usual Mississauga, 17 August: 18.9 µg/m³, 2.8× usual Mississauga, 18 August: 6.6 µg/m³, 1.0× usual Mississauga, 19 August: 15.7 µg/m³, 2.3× usual Waterdown Waterdown, 13 August: 3.9 µg/m³, 0.5× usual Waterdown, 14 August: 7.0 µg/m³, 1.0× usual Waterdown, 15 August: 12.3 µg/m³, 1.7× usual Waterdown, 16 August: 32.3 µg/m³, 4.4× usual Waterdown, 17 August: 18.3 µg/m³, 2.5× usual Waterdown, 18 August: 8.8 µg/m³, 1.2× usual Waterdown, 19 August: 15.0 µg/m³, 2.1× usual Kitchener Kitchener, 13 August: 3.6 µg/m³, 0.5× usual Kitchener, 14 August: 7.5 µg/m³, 1.0× usual Kitchener, 15 August: 14.9 µg/m³, 2.0× usual Kitchener, 16 August: 32.0 µg/m³, 4.4× usual Kitchener, 17 August: 20.3 µg/m³, 2.8× usual Kitchener, 18 August: 10.2 µg/m³, 1.4× usual Kitchener, 19 August: 17.3 µg/m³, 2.4× usual Brampton Brampton, 13 August: 3.5 µg/m³, 0.5× usual Brampton, 14 August: 9.8 µg/m³, 1.3× usual Brampton, 15 August: 14.7 µg/m³, 2.0× usual Brampton, 16 August: 31.6 µg/m³, 4.3× usual Brampton, 17 August: 19.7 µg/m³, 2.7× usual Brampton, 18 August: 6.0 µg/m³, 0.8× usual Brampton, 19 August: 16.7 µg/m³, 2.3× usual Toronto Toronto, 13 August: 3.8 µg/m³, 0.5× usual Toronto, 14 August: 8.6 µg/m³, 1.1× usual Toronto, 15 August: 12.8 µg/m³, 1.7× usual Toronto, 16 August: 31.6 µg/m³, 4.1× usual Toronto, 17 August: 19.2 µg/m³, 2.5× usual Toronto, 18 August: 5.5 µg/m³, 0.7× usual Toronto, 19 August: 16.5 µg/m³, 2.1× usual London London, 13 August: 5.3 µg/m³, 0.7× usual London, 14 August: 6.3 µg/m³, 0.8× usual London, 15 August: 14.2 µg/m³, 1.9× usual London, 16 August: 31.4 µg/m³, 4.2× usual London, 17 August: 17.3 µg/m³, 2.3× usual London, 18 August: 12.2 µg/m³, 1.6× usual London, 19 August: 16.1 µg/m³, 2.1× usual Guelph Guelph, 13 August: 3.7 µg/m³, 0.5× usual Guelph, 14 August: 7.6 µg/m³, 1.1× usual Guelph, 15 August: 14.5 µg/m³, 2.1× usual Guelph, 16 August: 31.2 µg/m³, 4.5× usual Guelph, 17 August: 21.7 µg/m³, 3.1× usual Guelph, 18 August: 8.8 µg/m³, 1.3× usual Guelph, 19 August: 17.3 µg/m³, 2.5× usual St. Thomas St. Thomas, 13 August: 4.7 µg/m³, 0.7× usual St. Thomas, 14 August: 8.1 µg/m³, 1.2× usual St. Thomas, 15 August: 9.6 µg/m³, 1.4× usual St. Thomas, 16 August: 30.3 µg/m³, 4.5× usual St. Thomas, 17 August: 17.6 µg/m³, 2.6× usual St. Thomas, 18 August: 12.3 µg/m³, 1.8× usual St. Thomas, 19 August: 12.8 µg/m³, 1.9× usual Brantford Brantford, 13 August: 4.0 µg/m³, 0.5× usual Brantford, 14 August: 7.1 µg/m³, 1.0× usual Brantford, 15 August: 12.2 µg/m³, 1.6× usual Brantford, 16 August: 28.8 µg/m³, 3.9× usual Brantford, 17 August: 19.6 µg/m³, 2.6× usual Brantford, 18 August: 10.7 µg/m³, 1.4× usual Brantford, 19 August: 13.5 µg/m³, 1.8× usual Hamilton Hamilton, 13 August: 3.8 µg/m³, 0.5× usual Hamilton, 14 August: 8.0 µg/m³, 1.0× usual Hamilton, 15 August: 13.2 µg/m³, 1.7× usual Hamilton, 16 August: 28.8 µg/m³, 3.6× usual Hamilton, 17 August: 17.5 µg/m³, 2.2× usual Hamilton, 18 August: 9.2 µg/m³, 1.2× usual Hamilton, 19 August: 14.0 µg/m³, 1.8× usual 13 Aug 14 15 16 17 18 19 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
North Bay Ontario, Canada 1 15 August 5.7 13× Greater Sudbury Ontario, Canada 1 15 August 6.0 13× Oakville Ontario, Canada 1 16 August 7.8 5.0× Barrie Ontario, Canada 1 16 August 7.9 4.8× Mississauga Ontario, Canada 1 16 August 6.8 4.8× Newmarket Ontario, Canada 1 16 August 7.7 4.7× Guelph Ontario, Canada 1 16 August 7.0 4.5× St. Thomas Ontario, Canada 1 16 August 6.8 4.5× Waterdown Ontario, Canada 1 16 August 7.3 4.4× Kitchener Ontario, Canada 1 16 August 7.3 4.4× Brampton Ontario, Canada 1 16 August 7.4 4.3× London Ontario, Canada 1 16 August 7.5 4.2× Toronto Ontario, Canada 1 16 August 7.7 4.1× Milton Ontario, Canada 1 16 August 8.3 4.1× Brantford Ontario, Canada 1 16 August 7.4 3.9× Hamilton Ontario, Canada 1 16 August 8.0 3.6×
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 Canada
Number 7 of 11 episodes in Canada since our records began, by cities reached.
North-western United States and Canada, August 2023 110 North-western United States and Canada, May 2023 42 North-eastern United States and Canada, September and October 2023 30 North-western United States and Canada, May 2023 24 North-western Canada and United States, August and September 2023 19 North-western Canada and United States, July 2023 17 Ontario, Canada, August 2023 16 Eastern Canada and United States, September 2023 9 Alberta and Saskatchewan, Canada, August 2023 9 Alberta and Saskatchewan, Canada, July 2023 9 North-eastern United States and Canada, April 2023 9 Bars: cities reached; colour: the level of the episode's highest daily reading.
Use this page SmogRank, Ontario, Canada, August 2023: 16 cities with PM2.5 at twice their usual or more, 16 August 2023, smogrank.com/episodes/2023-08-ontario-canada (accessed 2 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.
