City report · Ontario, Canada
St. Catharines Air quality today
Air quality in St. Catharines currently reads AQI 39 (Good): Air quality is satisfactory for everyone.
AQI 39
Air quality right now
Good
- PM2.5, fine particles (µg/m³)
- 7.0
- tree cover
- 32.8%
- trees in this area
- 103K
- more trees needed
- 0
Measured across a 2 km radius around Haig, St. Catharines, ON, Canada (12.57 km²), from a satellite image of Aug 28, 2026. Lower AQI is better: 0–50 is Good, above 300 is Hazardous.
St. Catharines · AQI 39 (Good)
St. Catharines's tree count comes to 102,735 trees across 12.53 km² of land, already at or above the 30% tree-cover level considered healthy for this area.
Air quality detail
Air quality in St. Catharines today: AQI 39, Good
Main pollutant: PM2.5 · Observed Nov 11, 11:00 local time via OpenAQ ground stations, US EPA index. Values in µg/m³.
Ground station · St. Catharines, 1.4 km away
Health signal
Air quality is satisfactory for everyone.
PM2.5
7.0
PM10
—
NO₂
22.6
O₃
—
SO₂
—
CO
—
Data: OpenAQ · AirNow
- Outdoor exercise
- A good day to be active outside
- Windows
- Open them to air the house
- Mask
- Not needed
- Air purifier
- Not needed
Over the last 7 days, the CAMS air-quality model put St. Catharines's daily AQI at 21 on average, from 11 on Nov 9 to an hourly peak of 41 on Nov 8.
This is the US EPA AQI. How it differs from Canada's AQHI
Where St. Catharines stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in St. Catharines: Healthy tree cover
32.8% tree cover against a 30% healthy-neighborhood target, across 12.53 km² of land.
Trees in this area
102,735
Target trees
102,735
More trees needed
0
CO₂ if planted / yr
0 kg
Deforestation · 2001–2025
How much forest has St. Catharines lost?
Since 2001, the area within 10 km of St. Catharines has lost about 39 hectares of forest (about 54 football pitches): under 1% of the forest it had in 2000. Most of it (67%) was deforestation, forest cleared for good, mainly for towns and roads.
2017: satellite photo from June 2017 of a 5 × 5 km area in the city center.
- Forest lost since 2001
- 39 haabout 54 football pitches
- Share of its forest
- under 1%of what there was in 2000
- Cleared for good
- 26 hadeforestation: turned into farms, mines or towns
The worst year was 2008, when about 4 hectares of forest were lost.
Hectares of forest lost each year
Show the figures as a table
| Year | Cleared for good | Can grow back | Total |
|---|---|---|---|
| 2001 | under 1 ha | under 1 ha | under 1 ha |
| 2002 | under 1 ha | under 1 ha | under 1 ha |
| 2003 | 2 ha | under 1 ha | 2 ha |
| 2004 | under 1 ha | under 1 ha | 2 ha |
| 2005 | under 1 ha | 1 ha | 2 ha |
| 2006 | under 1 ha | under 1 ha | under 1 ha |
| 2007 | under 1 ha | under 1 ha | 1 ha |
| 2008 | 4 ha | under 1 ha | 4 ha |
| 2009 | 1 ha | under 1 ha | 2 ha |
| 2010 | under 1 ha | under 1 ha | 1 ha |
| 2011 | under 1 ha | under 1 ha | under 1 ha |
| 2012 | under 1 ha | under 1 ha | 1 ha |
| 2013 | under 1 ha | under 1 ha | under 1 ha |
| 2014 | under 1 ha | under 1 ha | under 1 ha |
| 2015 | under 1 ha | under 1 ha | under 1 ha |
| 2016 | 1 ha | under 1 ha | 2 ha |
| 2017 | 3 ha | under 1 ha | 3 ha |
| 2018 | 2 ha | under 1 ha | 3 ha |
| 2019 | 2 ha | under 1 ha | 2 ha |
| 2020 | 2 ha | under 1 ha | 3 ha |
| 2021 | 3 ha | under 1 ha | 3 ha |
| 2022 | under 1 ha | under 1 ha | under 1 ha |
| 2023 | 1 ha | under 1 ha | 2 ha |
| 2024 | under 1 ha | under 1 ha | under 1 ha |
| 2025 | under 1 ha | 4 ha | 4 ha |
What is causing deforestation around St. Catharines?
- Towns and roadscleared for good33% · 13 ha
- Farms, pasture and plantationscleared for good32% · 13 ha
- Loggingcan grow back4.4% · 2 ha
Also: mining and energy, unknown causes.
Causes for 2025 are estimates, based on what caused forest loss in the same places up to 2024.
Forest gained and lost, 2000–2020
- Forest in 2000
- 6,300 ha
- Forest in 2020
- 6,460 ha
- Overall change
- +168 hamore forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around St. Catharines grew from about 6,300 hectares to 6,460 hectares, a net gain of about 168 hectares (+2.7%). New forest grew on about 295 hectares, while 127 hectares were lost.
These 2000 and 2020 maps, from the University of Maryland, count any land with trees taller than 5 m as forest, including plantations and orchards. Forest that was cut or burned and had grown back by 2020 counts in both years, so the loss here is smaller than the yearly figures.
These figures cover everything within 10 km of the city center, a wider area than the report above, because forest is usually lost at a city's edges.
Source: Hansen/UMD/Google/USGS/NASA, Global Forest Change (GFC-2025-v1.13); causes: WRI/Google DeepMind drivers of forest loss; both CC BY 4.0, summed by Airleaf for each area. Forest gained and lost 2000–2020: Potapov et al. 2022, UMD GLAD Global Land Cover and Land Use Change, CC BY 4.0. Images: contains modified Copernicus Sentinel data. How it's measured
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Frequently asked
Questions about St. Catharines
What is the air quality (AQI) in St. Catharines right now?
The latest reading for St. Catharines shows an AQI of 39 (Good), measured Nov 11, 11:00 local time by the St. Catharines ground monitoring station, 1.4 km away, via OpenAQ. The main pollutant is PM2.5. Air quality is satisfactory for everyone.
Is it safe to exercise outside in St. Catharines today?
At AQI 39 (Good): a good day to be active outside. Windows: open them to air the house. Masks: not needed. The reading changes through the day, so check again before a long run or ride.
What has the air quality in St. Catharines been like this week?
Over the last 7 days, the CAMS air-quality model put St. Catharines's daily AQI at 21 on average, from 11 on Nov 9 to an hourly peak of 41 on Nov 8. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
Is St. Catharines's AQI the same as Canada's AQHI?
No. Airleaf shows the US EPA Air Quality Index (AQI), the scale used by IQAir and most air-quality apps. Canada's Air Quality Health Index (AQHI), from Environment and Climate Change Canada, runs from 1 to 10 and above: 1–3 low risk, 4–6 moderate, 7–10 high and over 10 very high. It combines ozone, nitrogen dioxide and fine particles into one health-risk number, so it isn't a converted AQI, and the two can move differently, especially in wildfire smoke.
How much forest has the area around St. Catharines lost since 2001?
Since 2001, the area within 10 km of St. Catharines has lost about 39 hectares of forest (about 54 football pitches): under 1% of the forest it had in 2000. Most of it (67%) was deforestation, forest cleared for good, mainly for towns and roads. Comparing satellite maps from 2000 and 2020, the forest around St. Catharines grew from about 6,300 hectares to 6,460 hectares, a net gain of about 168 hectares (+2.7%). New forest grew on about 295 hectares, while 127 hectares were lost.
What is the tree count in St. Catharines?
St. Catharines has an estimated 102,735 trees across the 12.53 km² of land measured — 32.8% tree cover, already past the 30% tree-cover target set for this area.
How many more trees does St. Catharines need?
St. Catharines has already reached its tree-cover target, so no additional trees are needed to close the gap.
How are St. Catharines's air quality and tree cover measured?
Air quality is measured by ground monitoring stations near Haig, via OpenAQ; the 7-day trend is the Open-Meteo / CAMS model's estimate. Tree cover is measured from Sentinel-2 L2A (ESA Copernicus) via Earth Search satellite imagery at 10 m detail across a 2 km radius around Haig; the tree count is an estimate derived from that cover.
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