Air quality comparison · Canada, 351 km apart
Ottawa vs Toronto Air quality index (AQI) today
Ottawa has cleaner air than Toronto right now: AQI 19 (Good) against 58 (Moderate).
That puts them in different EPA bands, so the health advice differs today. Over the past 7 days, on modeled daily averages, Ottawa averaged AQI 26 against 28, and it was the cleaner of the two on 3 of those days. Ottawa has lost more forest since 2001. Ottawa has more tree cover.
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Ottawa19Toronto58
Head to head
Ottawa vs Toronto at a glance
Ottawa is ahead on 5 of 6 measures, and Toronto on 1. The better figure in each row is marked.
| Ottawa | Toronto | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 19 (better) | 58 |
| PM2.5Fine particles, µg/m³. | 1.9 (better) | 13 |
| Past week's averageUS AQI, 7 days. | 26 (better) | 28 |
| Forest lost since 2001Within 10 km of the center. | 302 ha | 16 ha (better) |
| Tree coverWithin 2 km of the center. | 22.4% (better) | 15.6% |
| Trees still neededTo reach a healthy canopy. | 22.2K (better) | 42.5K |
Air quality today
What is the air like in Ottawa and Toronto right now?
Ottawa has cleaner air than Toronto right now: AQI 19 (Good) against 58 (Moderate). Ozone is setting the index in Ottawa, and PM2.5 in Toronto.
Both readings come from nearby ground stations.
OttawaToronto
Concentrations at the same moment as the index above, for the pollutants both places report. Lower is better. The dark marks on the PM2.5 and PM10 rows show the WHO's 24-hour guidelines (15 and 45 µg/m³).
The past week
Which had cleaner air over the past 7 days?
Over the past 7 days, on modeled daily averages, Ottawa averaged AQI 26 against 28, and it was the cleaner of the two on 3 of those days. A single reading can catch a city on a bad afternoon; the week says whether it was the weather or the place.
- Cleaner days
- Ottawa3Toronto4
- Average AQI
- Ottawa26Toronto28
- Worst day, AQI
- Ottawa51Toronto35
The daily numbers (7 days)
| Day | Ottawa | Toronto |
|---|---|---|
| Nov 5 | 19 | 27 |
| Nov 6 | 28 | 27 |
| Nov 7 | 51 | 33 |
| Nov 8 | 34 | 35 |
| Nov 9 | 16 | 11 |
| Nov 10 | 34 | 26 |
| Nov 11 | 2 | 34 |
Daily averages from the CAMS atmospheric model for both places, so the week compares like with like. They can differ from today's reading at the top of the page wherever that comes from a ground station.
What it means today
Is it safe to go outside in Ottawa and Toronto today?
Ottawa (AQI 19, Good): Air quality is satisfactory for everyone.
Toronto (AQI 58, Moderate): Unusually sensitive people should consider limiting long outdoor exertion.
Exercise outdoors
- Ottawa
- A good day to be active outside.
- Toronto
- Fine for most people; unusually sensitive people should take long or hard exercise easier.
Windows
- Ottawa
- Open them to air the house.
- Toronto
- Fine to open; close them if you are sensitive to pollution.
Masks
- Ottawa
- Not needed.
- Toronto
- Not needed for most people.
Air purifier
- Ottawa
- Not needed.
- Toronto
- Worth running if you are sensitive.
Against everywhere else
How do Ottawa and Toronto compare with the rest of the world?
Right now Ottawa's air is cleaner than 89% of the 5,420 places Airleaf tracks, and Toronto's is cleaner than 50%. Within Canada, that is 67% and 10% of its 59 measured places.
Cleaner air than…
- Ottawa
- Beats 89%
- Toronto
- Beats 50%
More tree cover than…
- Ottawa
- Beats 52%
- Toronto
- Beats 36%
Includes model estimates as well as station readings, so it can differ from our most polluted and cleanest air rankings, which use station readings only.
Deforestation · 2001–2025
Which has lost more forest, Ottawa or Toronto?
Ottawa has lost more: about 302 ha of forest within 10 km of its center from 2001 to 2025, against 16 ha around Toronto. 257 ha of that was cleared for good, for farms, mines or towns.
Measured within 10 km of each center, from the yearly satellite maps of forest loss: a wider circle than the one for tree cover, because forest is usually lost at a city's edges.
Worst year: 2022, with 44 ha lost.
Worst year: 2008, with 3 ha lost.
| Ottawa | Toronto | |
|---|---|---|
| Forest lost since 2001Cleared, burned or logged. | 302 ha | 16 ha (better) |
| Share of its forestOf what it had in 2000. | 4.1% | under 1% (better) |
| Cleared for goodTurned into farms, mines or towns. | 257 ha | 11 ha (better) |
| Recent trend2021–2025 against the five years before. | Too little to call | Too little to call |
| Main known cause | Towns and roads (85%) | Towns and roads (67%) |
Satellite timelapses
Watch both change, year by year
A clear satellite photo a year of the land around each city. Press play, turn on the forest cleared since the first year, or drag the before and after.
Ottawa
2017: satellite photo from September 2017 of a 5 × 5 km area about 7 km west of the city center.
Toronto
2017: satellite photo from August 2017 of a 5 × 5 km area in the city center.
Trees
Which has more trees, Ottawa or Toronto?
Ottawa has more tree cover: 22.4% of the land within 2 km of its center against 15.6% around Toronto, or about 65,305 trees against 46,068.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Ottawa | Toronto | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 65.3K (better) | 46.1K |
| Trees still neededTo reach the target. Fewer is better. | 22.2K (better) | 42.5K |
| CO₂ absorbed each yearBy the trees already standing. | 1.4M kg (better) | 1.0M kg |
Tree cover on the satellite image
The same 2 km radius around each center, with the tree cover the satellite found marked on it.
Reading these numbers
How this comparison is made
Air quality index
The US EPA index, computed from current pollutant concentrations: ground stations where a place has them nearby, and the CAMS atmospheric model everywhere else. It moves hour to hour, so it is a snapshot rather than a verdict on either place. The guideline marks are from the WHO's 2021 air quality guidelines.
Trees and forest
Tree cover is the share of ground under canopy within 2 km of each center, read from Sentinel-2 satellite imagery at 10 m detail. It measures that circle, not the whole municipality, which is what makes the two comparable. Forest loss comes from the University of Maryland's Global Forest Change maps.
More on the method on the About Airleaf page.
Frequently asked
Ottawa vs Toronto: your questions answered
Is Ottawa cleaner than Toronto?
On air quality, yes, right now: Ottawa reads AQI 19 against 58, a gap of 39 points on the US EPA index. This is a live reading rather than an annual average, so it can reverse within a day. Over the past 7 days, on modeled daily averages, Ottawa averaged AQI 26 against 28, and it was the cleaner of the two on 3 of those days.
Is it safe to exercise outdoors in Ottawa and Toronto today?
In Ottawa, at AQI 19: Air quality is satisfactory for everyone. In Toronto, at AQI 58: Unusually sensitive people should consider limiting long outdoor exertion.
Which has lost more forest, Ottawa or Toronto?
Ottawa has lost more: about 302 ha of forest within 10 km of its center from 2001 to 2025, against 16 ha around Toronto. 257 ha of that was cleared for good, for farms, mines or towns.
Which has more trees, Ottawa or Toronto?
Ottawa has more tree cover: 22.4% of the land within 2 km of its center against 15.6% around Toronto, or about 65,305 trees against 46,068. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Ottawa and Toronto need?
Ottawa needs about 22,157 more to reach its canopy target of 30%, and Toronto about 42,525 to reach 30%. The target starts at 30% of the land and rises where air quality is poor.
Are Ottawa and Toronto measured the same way?
The method is the same: the US EPA index for air, and Sentinel-2 satellite imagery at 10 m detail over an identical radius for trees. Both readings come from nearby ground stations. Nothing is adjusted for population, city limits or climate.
How often does the Ottawa vs Toronto comparison update?
The air readings refresh about once an hour, and each reading's local time is shown at the top of the page. Tree cover comes from the latest clear satellite image of each area (Sep 11, 2026 and Aug 18, 2026), and the forest figures are published yearly.
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