Air Quality in Toronto, Ontario — Live
Live readings from PurpleAir sensors across Toronto — with free alerts the moment the air turns.
AQI 17 from 4 PurpleAir sensors · Trending up · data from PurpleAir
As of , the air quality in Toronto, Ontario is AQI 17 — Good and rising — with PM2.5 at 3.0 µg/m³, the median of 4 live PurpleAir sensors reading 1 to 19. Canairy's verdict: Breathe easy.
For scale, that PM2.5 reading is below the World Health Organization's 24-hour guideline of 15 µg/m³. The WHO figure is a daily average and this is a live reading, so read it as a sense of magnitude rather than a formal exceedance — a brief spike and a bad day are not the same thing. More on the WHO guidelines
Pollen today in Toronto: grass pollen is the strongest of the three at a none level, from Google's pollen forecast. Canairy shows the tree, grass and weed forecast beside the air reading on every plan, including the free one.
Free to download · Live data from PurpleAir & public monitors
Live PurpleAir sensor map for Toronto and Mississauga, Scarborough, North York, Etobicoke. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Toronto
The sensors Canairy reads in Toronto agree right now — all 4 sit in the Good band, a 18-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 0.9 mi NW | 1 | Good |
| 2.1 mi NE | 19 | Good |
| 2.2 mi SSE | 11 | Good |
| 4.1 mi W | 17 | Good |
Toronto's air has two very different problems, and only one of them is getting better. The city sits on the north shore of Lake Ontario in the middle of a dense grid of highways, and exhaust from cars, trucks and other on-road vehicles is now the largest single source of local air pollution here — more than half of Toronto's air pollution comes from sources inside the city's own boundaries. The other problem arrives from hundreds of kilometres away. On 28 June 2023, smoke from forest fires in northeastern Ontario and Quebec made Toronto the most polluted major city in the world, with visibility down to roughly a kilometre. Neither problem shows up in the weather forecast, and both can change the air on your street within an hour.
What Canairy does for Toronto
A clear verdict
Not just a number — a plain-English call for Toronto: open the windows, or keep them shut.
Smoke alerts
A push or text the moment the air crosses your threshold — and again when it clears.
A heads-up before it's bad
Trend alerts catch the air turning, so you can close up the house before the smoke settles in.
Every place you care about
Home, work, the kids' school — across Toronto or across the country, on one screen.
The summer smog days went away with the coal plants
Anyone who lived here in the 2000s remembers smog advisories as a normal part of July. Ontario recorded 53 smog days in 2005, its worst year on record. Then the province spent seventeen years and three governments closing its coal-fired generating stations, ending with the Nanticoke Generating Station on Lake Erie, the largest of them, which burned its last coal in April 2014. Ontario became the first jurisdiction in North America to remove coal from its electricity system entirely. The phase-out cut about 17 per cent of the province's emissions, roughly the equivalent of taking seven million cars off the road.
The air responded almost immediately. Ontario logged zero smog days in 2014, and 2015 was the first year since 1970 without a single smog warning anywhere in southern Ontario. That is worth holding onto when a bad-air day arrives: the baseline in Toronto is genuinely better than it was twenty years ago, and the days that do go bad now go bad for different reasons.
June 2023, when Toronto had the worst air in the world
On 28 June 2023, IQAir ranked Toronto the most polluted major city on the planet — briefly the only city anywhere rated in the very unhealthy band. The AQI touched 300 at its peak and topped 200 for the first time that year, and visibility across downtown fell to about a kilometre. Environment Canada had special air quality statements out over more than twenty areas of southern Ontario at once, from Hamilton, Mississauga and Brampton through Vaughan, Markham, Oakville and Burlington to Niagara, Barrie, Peterborough, Windsor and London. The smoke came from fires burning in northeastern Ontario and Quebec, hundreds of kilometres from any of it.
The city treats it as a recurring hazard now rather than a freak event. Toronto Public Health maintains a Wildfire Smoke Response Strategy that is reviewed and updated every year, and in 2024 launched a Cleaner Air Spaces Network — civic centres fitted with MERV13 filtration where people can go when the outdoor air is bad. If you have asthma, a heart condition, or small kids, knowing which building near you is on that list before smoke season is a reasonable thing to do in May rather than in June.
The 401 runs through the middle of it
The stretch of Highway 401 that crosses Toronto is the busiest highway in North America, carrying commuters and commercial trucks in the same lanes all day. That traffic is not an abstract problem. Health Canada attributed 170 premature deaths in Toronto in 2015 to traffic pollution alone, plus another 43 in neighbouring Peel Region. About a third of Canadians live within 250 metres of a major road, and Toronto has a great many people in exactly that band — along the 401, the Gardiner, the DVP, and the big arterials in between.
There is a layer of this that no consumer sensor sees. A study tracking ultrafine particles in Toronto and Montreal from 2001 to 2016, published in the American Journal of Respiratory and Critical Care Medicine, linked outdoor ultrafine particles to roughly 600 non-accidental deaths a year in Toronto, with respiratory disease deaths up 17.4 per cent and coronary artery disease deaths up 9.4 per cent. Ultrafine particles are smaller than the PM2.5 that air-quality sensors measure, and they were not routinely recorded before that work. It is a reason to treat a merely acceptable number beside a busy road with a little scepticism, and a reason not to jog along the 401 shoulder because the AQI said 42.
Toronto air quality FAQ
What is the air quality in Toronto right now?
As of September 11, 2026 at 1:37 AM EDT, the air quality in Toronto, Ontario is AQI 17 — Good — with PM2.5 at 3.0 µg/m³, the median of 4 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is there smoke in Toronto today?
Almost always wildfire smoke that has travelled a long way, most often from fires in northern Ontario, Quebec or the Prairies. In late June 2023, smoke from fires in northeastern Ontario and Quebec pushed Toronto to the worst air quality of any major city in the world and dropped visibility to about a kilometre, with special air quality statements covering more than twenty communities across southern Ontario at once. Wind direction matters more than distance: there can be nothing burning within five hundred kilometres and the sky can still turn orange by lunchtime.
Canada reports the AQHI — why does this page show a different number?
Environment Canada reports air quality as the Air Quality Health Index, a 1-to-10+ scale of short-term health risk. This page does not show the AQHI. It shows the US EPA Air Quality Index, the 0-to-500 scale used by PurpleAir and most air-quality apps, so a Toronto reading is directly comparable with any other city on the map. The reason is practical: the AQHI is calculated from three pollutants together — ground-level ozone, nitrogen dioxide and fine particulate matter — and PurpleAir sensors measure only the fine particles. On a smoky day, when particles dominate, the two scales tell much the same story. On a hot, still, ozone-heavy afternoon the AQHI can read higher than a particle-only number suggests, so check Environment Canada's AQHI alongside this page if ozone is your particular concern.
Does living near the 401 or the Gardiner actually matter?
The evidence says yes. The city names on-road vehicle exhaust as the largest local source of Toronto's air pollution, the section of the 401 through Toronto is the busiest highway in North America, and Health Canada attributed 170 premature deaths in Toronto in 2015 to traffic pollution alone. Roughly a third of Canadians live within 250 metres of a major road. A sensor on your own block is worth more here than a regional average, because traffic pollution falls off sharply with distance from the road.
What the AQI numbers mean
| AQI | Category | What it means for you |
|---|---|---|
| 0–50 | Good | Open the windows. Great for outdoor activity. |
| 51–100 | Moderate | Sensitive groups may want to take it slower outside. |
| 101–150 | Unhealthy for Sensitive Groups | Kids, elderly, and respiratory conditions stay closer to home. |
| 151–200 | Unhealthy | Skip outdoor exercise. Close windows. |
| 201–300 | Very Unhealthy | Limit time outside. N95 if you must go. |
| 301+ | Hazardous | Health emergency. Stay inside, run filtration if you have it. |
Canairy lets you tighten these bands if you’re more sensitive than the EPA default, so an alert can fire before the official category changes. How to read the Air Quality Index
Where these readings come from
The AQI at the top of this page is the median of the 4 curated PurpleAir sensors Canairy tracks in and around Toronto, with outliers set aside so that one sensor brought indoors — or parked beside a barbecue — cannot set the number for a whole city. Every sensor behind it is listed above with its distance and bearing from the city center. There is no black box here.
In the app, a place you save resolves the same way first. When no neighborhood sensor is reporting it falls back to the nearest EPA AirNow monitor, and anything modeled rather than measured is labelled a regional estimate rather than passed off as a sensor reading. How low-cost sensors compare to regulatory monitors
About Canairy
Canairy is free to download. The free plan covers one saved place with live readings, a plain-English verdict, and push alerts when the air crosses a threshold you choose. Paid plans add more places, faster refreshes, and SMS alerts. It is built by two parents in Sonoma County, California, who got tired of guessing whether it was safe to send the kids outside. Why we built it
Go deeper
Air quality near Toronto
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