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St. Thomas, Ontario climate
Dfb Warm-summer humid continental
St. Thomas has a strongly seasonal cool-temperate climate (Warm-summer humid continental, Köppen Dfb). The hottest month is July with an average daily high near 81°F, while the coldest is January averaging around 17°F at night. Precipitation is fairly even year-round, totalling about 36 inches. Winters bring significant snowfall (45 inches 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)St. Thomas climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 31 | 34 | 43 | 55 | 68 | 77 | 81 | 79 | 72 | 60 | 47 | 37 |
| Avg temp (°F) | 24 | 26 | 34 | 45 | 57 | 67 | 70 | 69 | 62 | 51 | 40 | 31 |
| Avg low (°F) | 17 | 18 | 26 | 36 | 47 | 56 | 60 | 59 | 52 | 42 | 33 | 24 |
| Precipitation (in) | 3.3 | 2.3 | 2.5 | 3.4 | 3.1 | 3.1 | 3.1 | 2.6 | 3.3 | 3.5 | 3.0 | 2.5 |
| Snowfall (in) | 14.9 | 10.8 | 6.3 | 1.1 | — | — | — | — | — | 0.1 | 3.1 | 8.3 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°F) | 31 | 34 | 43 | 55 | 68 | 77 |
| Avg temp (°F) | 24 | 26 | 34 | 45 | 57 | 67 |
| Avg low (°F) | 17 | 18 | 26 | 36 | 47 | 56 |
| Precipitation (in) | 3.3 | 2.3 | 2.5 | 3.4 | 3.1 | 3.1 |
| Snowfall (in) | 14.9 | 10.8 | 6.3 | 1.1 | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°F) | 81 | 79 | 72 | 60 | 47 | 37 |
| Avg temp (°F) | 70 | 69 | 62 | 51 | 40 | 31 |
| Avg low (°F) | 60 | 59 | 52 | 42 | 33 | 24 |
| Precipitation (in) | 3.1 | 2.6 | 3.3 | 3.5 | 3.0 | 2.5 |
| Snowfall (in) | — | — | — | 0.1 | 3.1 | 8.3 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 78 | 77 | 75 | 72 | 70 | 64 | 57 | 57 | 58 | 68 | 75 | 79 |
| Relative humidity (%) | 88 | 86 | 81 | 76 | 73 | 70 | 67 | 68 | 71 | 77 | 83 | 87 |
| Wind speed (mph) | 10.5 | 10.1 | 9.4 | 9.0 | 7.4 | 6.5 | 6.1 | 5.9 | 6.6 | 7.8 | 8.7 | 9.4 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 78 | 77 | 75 | 72 | 70 | 64 |
| Relative humidity (%) | 88 | 86 | 81 | 76 | 73 | 70 |
| Wind speed (mph) | 10.5 | 10.1 | 9.4 | 9.0 | 7.4 | 6.5 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 57 | 57 | 58 | 68 | 75 | 79 |
| Relative humidity (%) | 67 | 68 | 71 | 77 | 83 | 87 |
| Wind speed (mph) | 6.1 | 5.9 | 6.6 | 7.8 | 8.7 | 9.4 |
Methodology & sources
Temperature & precipitation — 1991–2020 normals computed from 26 years of daily observations at ST Thomas Wpcp, a weather station, about 2 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.