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Sarnia, Ontario climate
Dfb Warm-summer humid continental
Sarnia has a strongly seasonal cool-temperate climate (Warm-summer humid continental, Köppen Dfb). The hottest month is July with an average daily high near 79°F, while the coldest is January averaging around 19°F at night. Precipitation is fairly even year-round, totalling about 36 inches. Winters bring significant snowfall (35 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)Sarnia climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 31 | 33 | 41 | 53 | 65 | 75 | 79 | 78 | 72 | 60 | 47 | 37 |
| Avg temp (°F) | 25 | 26 | 34 | 45 | 56 | 66 | 70 | 69 | 63 | 52 | 41 | 31 |
| Avg low (°F) | 19 | 19 | 26 | 36 | 47 | 57 | 62 | 60 | 54 | 44 | 34 | 25 |
| Precipitation (in) | 2.6 | 2.2 | 2.6 | 3.4 | 3.5 | 3.1 | 3.5 | 2.9 | 3.1 | 3.2 | 3.0 | 2.8 |
| Snowfall (in) | 10.1 | 8.8 | 5.3 | 1.4 | — | — | — | — | — | 0.1 | 1.8 | 8.0 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°F) | 31 | 33 | 41 | 53 | 65 | 75 |
| Avg temp (°F) | 25 | 26 | 34 | 45 | 56 | 66 |
| Avg low (°F) | 19 | 19 | 26 | 36 | 47 | 57 |
| Precipitation (in) | 2.6 | 2.2 | 2.6 | 3.4 | 3.5 | 3.1 |
| Snowfall (in) | 10.1 | 8.8 | 5.3 | 1.4 | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°F) | 79 | 78 | 72 | 60 | 47 | 37 |
| Avg temp (°F) | 70 | 69 | 63 | 52 | 41 | 31 |
| Avg low (°F) | 62 | 60 | 54 | 44 | 34 | 25 |
| Precipitation (in) | 3.5 | 2.9 | 3.1 | 3.2 | 3.0 | 2.8 |
| Snowfall (in) | — | — | — | 0.1 | 1.8 | 8.0 |
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 (%) | 86 | 84 | 79 | 75 | 74 | 73 | 71 | 72 | 73 | 76 | 80 | 84 |
| Wind speed (mph) | 11.1 | 10.2 | 9.6 | 9.4 | 7.7 | 6.7 | 6.3 | 6.3 | 7.3 | 9.0 | 10.1 | 10.5 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 78 | 77 | 75 | 72 | 70 | 64 |
| Relative humidity (%) | 86 | 84 | 79 | 75 | 74 | 73 |
| Wind speed (mph) | 11.1 | 10.2 | 9.6 | 9.4 | 7.7 | 6.7 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 57 | 57 | 58 | 68 | 75 | 79 |
| Relative humidity (%) | 71 | 72 | 73 | 76 | 80 | 84 |
| Wind speed (mph) | 6.3 | 6.3 | 7.3 | 9.0 | 10.1 | 10.5 |
Methodology & sources
Temperature & precipitation — 1991–2020 normals computed from 30 years of daily observations at New Glasgow, a weather station, about 81 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.