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Thunder Bay, Ontario climate
Dfb Warm-summer humid continental
Thunder Bay has a strongly seasonal cold-temperate climate (Warm-summer humid continental, Köppen Dfb). The hottest month is July with an average daily high near 25°C, while the coldest is January averaging around −21°C at night. Around 760 mm of precipitation falls each year, peaking in July (95 mm) and easing off in February (29 mm). Snowfall is heavy (185 cm of snow per year on average).
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation split into rain and snow · 1991–2020 normals · hover a month for the exact figuresHours of sunshine per day
Estimated sunny hours each month — daylight length × clear-sky fraction · 1991–2020 monthly cloud cover (NASA POWER)Thunder Bay climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | −8 | −4 | 2 | 10 | 17 | 22 | 25 | 24 | 19 | 11 | 2 | −5 |
| Avg temp (°C) | −14 | −12 | −5 | 2 | 9 | 15 | 17 | 17 | 12 | 5 | −3 | −10 |
| Avg low (°C) | −21 | −19 | −12 | −5 | 1 | 7 | 10 | 9 | 5 | −1 | −7 | −16 |
| Precipitation (mm) | 41 | 29 | 37 | 64 | 84 | 89 | 95 | 70 | 78 | 74 | 55 | 43 |
| Snowfall (cm) | 40 | 27 | 23 | 22 | 1 | — | — | — | 0 | 5 | 28 | 39 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | −8 | −4 | 2 | 10 | 17 | 22 |
| Avg temp (°C) | −14 | −12 | −5 | 2 | 9 | 15 |
| Avg low (°C) | −21 | −19 | −12 | −5 | 1 | 7 |
| Precipitation (mm) | 41 | 29 | 37 | 64 | 84 | 89 |
| Snowfall (cm) | 40 | 27 | 23 | 22 | 1 | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 25 | 24 | 19 | 11 | 2 | −5 |
| Avg temp (°C) | 17 | 17 | 12 | 5 | −3 | −10 |
| Avg low (°C) | 10 | 9 | 5 | −1 | −7 | −16 |
| Precipitation (mm) | 95 | 70 | 78 | 74 | 55 | 43 |
| Snowfall (cm) | — | — | 0 | 5 | 28 | 39 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 68 | 66 | 67 | 68 | 72 | 71 | 66 | 64 | 67 | 74 | 76 | 71 |
| Relative humidity (%) | 97 | 96 | 84 | 72 | 71 | 74 | 75 | 74 | 77 | 80 | 84 | 93 |
| Wind speed (mph) | 3.1 | 3.2 | 2.8 | 2.3 | 1.4 | 1.0 | 1.0 | 1.2 | 1.5 | 1.9 | 2.4 | 2.9 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 68 | 66 | 67 | 68 | 72 | 71 |
| Relative humidity (%) | 97 | 96 | 84 | 72 | 71 | 74 |
| Wind speed (mph) | 3.1 | 3.2 | 2.8 | 2.3 | 1.4 | 1.0 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 66 | 64 | 67 | 74 | 76 | 71 |
| Relative humidity (%) | 75 | 74 | 77 | 80 | 84 | 93 |
| Wind speed (mph) | 1.0 | 1.2 | 1.5 | 1.9 | 2.4 | 2.9 |
Methodology & sources
Temperature & precipitation — 1991–2020 normals computed from 23 years of daily observations at Flint, a weather station, about 32 km from the city centre. The underlying daily records come from NOAA's global station network.
Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.