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Cornwall, Ontario climate
Dfa Hot-summer humid continental
Cornwall has a strongly seasonal cool-temperate climate (Hot-summer humid continental, Köppen Dfa). The hottest month is July with an average daily high near 27°C, while the coldest is January averaging around −12°C at night. Precipitation is fairly even year-round, totalling about 999 mm. Snowfall is heavy (199 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)Cornwall climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | −4 | −2 | 3 | 12 | 20 | 25 | 27 | 26 | 22 | 14 | 7 | 0 |
| Avg temp (°C) | −8 | −6 | −1 | 7 | 14 | 19 | 22 | 21 | 17 | 10 | 3 | −4 |
| Avg low (°C) | −12 | −11 | −5 | 2 | 9 | 14 | 17 | 16 | 12 | 6 | 0 | −7 |
| Precipitation (mm) | 78 | 63 | 63 | 87 | 86 | 94 | 96 | 85 | 92 | 101 | 78 | 77 |
| Snowfall (cm) | 50 | 48 | 34 | 10 | 0 | — | — | — | — | 1 | 15 | 43 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | −4 | −2 | 3 | 12 | 20 | 25 |
| Avg temp (°C) | −8 | −6 | −1 | 7 | 14 | 19 |
| Avg low (°C) | −12 | −11 | −5 | 2 | 9 | 14 |
| Precipitation (mm) | 78 | 63 | 63 | 87 | 86 | 94 |
| Snowfall (cm) | 50 | 48 | 34 | 10 | 0 | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 27 | 26 | 22 | 14 | 7 | 0 |
| Avg temp (°C) | 22 | 21 | 17 | 10 | 3 | −4 |
| Avg low (°C) | 17 | 16 | 12 | 6 | 0 | −7 |
| Precipitation (mm) | 96 | 85 | 92 | 101 | 78 | 77 |
| Snowfall (cm) | — | — | — | 1 | 15 | 43 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 69 | 64 | 63 | 66 | 66 | 63 | 58 | 58 | 58 | 69 | 72 | 73 |
| Relative humidity (%) | 92 | 91 | 85 | 78 | 77 | 79 | 79 | 77 | 76 | 80 | 84 | 90 |
| Wind speed (km/h) | 4.8 | 5.8 | 4.7 | 2.9 | 1.7 | 1.5 | 1.5 | 1.4 | 1.5 | 1.5 | 1.8 | 2.8 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 69 | 64 | 63 | 66 | 66 | 63 |
| Relative humidity (%) | 92 | 91 | 85 | 78 | 77 | 79 |
| Wind speed (km/h) | 4.8 | 5.8 | 4.7 | 2.9 | 1.7 | 1.5 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 58 | 58 | 58 | 69 | 72 | 73 |
| Relative humidity (%) | 79 | 77 | 76 | 80 | 84 | 90 |
| Wind speed (km/h) | 1.5 | 1.4 | 1.5 | 1.5 | 1.8 | 2.8 |
Methodology & sources
Temperature & precipitation — 1991–2020 normals computed from 30 years of daily observations at Cornwall, 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.