City report · Ontario, Canada
Thunder Bay Air quality today
Air quality in Thunder Bay currently reads AQI 23 (Good): Air quality is satisfactory for everyone.
AQI 23
Air quality right now
Good
- PM2.5, fine particles (µg/m³)
- 4.1
- tree cover
- 29.7%
- trees in this area
- 86.0K
- more trees needed
- 869
Measured across a 2 km radius around Thunder Bay, 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.
Thunder Bay · AQI 23 (Good)
Thunder Bay's tree count comes to 86,027 trees across 11.59 km² of land, 0 points below the 30% tree-cover level considered healthy for this area, so roughly 869 more trees would close the gap.
Air quality detail
Air quality in Thunder Bay today: AQI 23, Good
Main pollutant: PM2.5 · Observed Nov 11, 10:00 local time via World Air Quality Index Project ground stations, US EPA index. Values in µg/m³.
Ground station · Thunder Bay, Ontario, Canada, 3 km away
Health signal
Air quality is satisfactory for everyone.
PM2.5
4.1
PM10
—
NO₂
—
O₃
—
SO₂
—
CO
—
Data: World Air Quality Index Project, Air Quality Ontario - the Ontario Ministry of the Environment and Climate Change
- 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 Thunder Bay's daily AQI at 14 on average, from 2 on Nov 4 to an hourly peak of 55 on Nov 9.
This is the US EPA AQI. How it differs from Canada's AQHI
Where Thunder Bay stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in Thunder Bay: Below target
29.7% tree cover against a 30% healthy-neighborhood target, across 11.59 km² of land.
Trees in this area
86,027
Target trees
86,896
More trees needed
869
CO₂ if planted / yr
19.1 t
Deforestation · 2001–2025
How much forest has Thunder Bay lost?
Since 2001, the area within 10 km of Thunder Bay has lost about 877 hectares of forest (about 1,200 football pitches): 6.8% of the forest it had in 2000. Most of it (60%) was deforestation, forest cleared for good, mainly for towns and roads.
2017: satellite photo from July 2017 of a 5 × 5 km area about 7 km west of the city center.
- Forest lost since 2001
- 877 haabout 1,200 football pitches
- Share of its forest
- 6.8%of what there was in 2000
- Cleared for good
- 524 hadeforestation: turned into farms, mines or towns
The worst year was 2006, when about 91 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 | 15 ha | 6 ha | 21 ha |
| 2002 | 30 ha | 6 ha | 36 ha |
| 2003 | 18 ha | 5 ha | 23 ha |
| 2004 | 18 ha | 5 ha | 23 ha |
| 2005 | 13 ha | 21 ha | 33 ha |
| 2006 | 41 ha | 51 ha | 91 ha |
| 2007 | 21 ha | 9 ha | 29 ha |
| 2008 | 13 ha | 5 ha | 18 ha |
| 2009 | 11 ha | 12 ha | 23 ha |
| 2010 | 23 ha | 11 ha | 34 ha |
| 2011 | 52 ha | 3 ha | 55 ha |
| 2012 | 21 ha | 65 ha | 87 ha |
| 2013 | 37 ha | 4 ha | 41 ha |
| 2014 | 28 ha | 26 ha | 54 ha |
| 2015 | 39 ha | 8 ha | 47 ha |
| 2016 | 10 ha | 4 ha | 14 ha |
| 2017 | 67 ha | 9 ha | 76 ha |
| 2018 | 13 ha | 6 ha | 18 ha |
| 2019 | 4 ha | under 1 ha | 4 ha |
| 2020 | 6 ha | under 1 ha | 7 ha |
| 2021 | 8 ha | 3 ha | 11 ha |
| 2022 | 18 ha | 69 ha | 87 ha |
| 2023 | 6 ha | 25 ha | 31 ha |
| 2024 | 10 ha | under 1 ha | 10 ha |
| 2025 | 5 ha | under 1 ha | 5 ha |
What is causing deforestation around Thunder Bay?
- Towns and roadscleared for good43% · 379 ha
- Loggingcan grow back37% · 328 ha
- Farms, pasture and plantationscleared for good10% · 88 ha
Also: mining and energy, storms, floods and other natural causes, 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
- 11,100 ha
- Forest in 2020
- 10,300 ha
- Overall change
- −805 haless forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around Thunder Bay shrank from about 11,100 hectares to 10,300 hectares, a net loss of about 805 hectares (−7.2%). New forest grew on about 179 hectares, but 984 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
In the same region
Measured cities near Thunder Bay
Same 2 km radius, same index — so they compare directly.
- Green Bay439.7 km
United States
- Tree cover
- 28%
- Air quality
- 10
- Saint Paul481.7 km
United States
- Tree cover
- 27%
- Air quality
- 21
- Minneapolis486.5 km
United States
- Tree cover
- 19%
- Air quality
- 27
- Rochester544.4 km
United States
- Tree cover
- 42%
- Air quality
- 23
- Fargo589.0 km
United States
- Tree cover
- 38%
- Air quality
- 22
- Madison590.4 km
United States
- Tree cover
- 31%
- Air quality
- 31
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Frequently asked
Questions about Thunder Bay
What is the air quality (AQI) in Thunder Bay right now?
The latest reading for Thunder Bay shows an AQI of 23 (Good), measured Nov 11, 10:00 local time by the Thunder Bay, Ontario, Canada ground monitoring station, 3 km away, via OpenAQ. The main pollutant is PM2.5. Air quality is satisfactory for everyone.
Is it safe to exercise outside in Thunder Bay today?
At AQI 23 (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 Thunder Bay been like this week?
Over the last 7 days, the CAMS air-quality model put Thunder Bay's daily AQI at 14 on average, from 2 on Nov 4 to an hourly peak of 55 on Nov 9. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
Is Thunder Bay'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 Thunder Bay lost since 2001?
Since 2001, the area within 10 km of Thunder Bay has lost about 877 hectares of forest (about 1,200 football pitches): 6.8% of the forest it had in 2000. Most of it (60%) was deforestation, forest cleared for good, mainly for towns and roads. Comparing satellite maps from 2000 and 2020, the forest around Thunder Bay shrank from about 11,100 hectares to 10,300 hectares, a net loss of about 805 hectares (−7.2%). New forest grew on about 179 hectares, but 984 hectares were lost.
What is the tree count in Thunder Bay?
Thunder Bay has an estimated 86,027 trees across the 11.59 km² of land measured — 29.7% tree cover, 0 percentage points short of the 30% tree-cover target set for this area.
How many more trees does Thunder Bay need?
Thunder Bay needs roughly 869 more trees to close a 0-point shortfall against its 30% tree-cover target — about 19.1 t of extra CO₂ absorbed per year once grown.
How are Thunder Bay's air quality and tree cover measured?
Air quality is measured by ground monitoring stations near Thunder Bay, 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 Thunder Bay; the tree count is an estimate derived from that cover.
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