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Cornwall (ON) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Cornwall.
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Climate overview of Cornwall
The climate in Cornwall, Ontario, Canada, is marked by large temperature swings across the seasons, ranging from 27°C (81°F) in July to -4°C (25°F) in January.
Rain/snowfall is high, totalling around 1006 mm (40 in) per year. October is the wettest month and March the driest. The city also experiences warm summers and very cold winters.
Cornwall Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Cornwall - and find the best time to visit.
Monthly Temperature in Cornwall
In Cornwall, temperatures differ significantly between summer and winter months. Average maximum daytime temperatures range from a comfortable 27°C (81°F) in July, the warmest time of the year, to a very cold -4°C (25°F) during cooler months like January.
At night, you can expect temperatures ranging from 16°C (61°F) in July to around -12°C (10°F) during January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Cornwall
Cornwall experiences significant rain/snowfall throughout the year, averaging 1006 mm (40 in) of precipitation annually. While rainfall varies throughout the year, each season offers its own charm. October brings wetter days averaging 115 mm (4.5 in) of precipitation, spread over 16 rainy days.
In contrast, the driest month March experiences a drier climate, with about 57 mm (2.2 in) of snow/rainfall spread across 13 snowy/rainy days. For more details, please visit our Cornwall Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Best Time to Visit Cornwall
For comfortable weather, consider visiting Cornwall in May, July, August and September. Conditions are usually least favourable in January, February, March, November and December.
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
Jan
very cold
Feb
very cold
Mar
cold
Apr
mixed
May
excellent
Jun
very good
Jul
excellent
Aug
excellent
Sep
excellent
Oct
mixed
Nov
cold
Dec
cold
- Best overall: May, July, August and September
- Warmest weather: July and August
- Seasonal pattern: Warm summers and very cold winters
- Coldest conditions: January, with freezing nights around -12°C (10°F).
Frequently asked questions about the climate in Cornwall
What is the best time to visit Cornwall?
May, July, August and September typically offer the most optimal weather in Cornwall. In contrast, January, February, March, November and December tend to have less optimal conditions. Cornwall has warm summers and very cold winters.
What temperatures can I expect in Cornwall?
Daytime highs range from -4°C (25°F) in January to 27°C (81°F) in July. Nighttime lows range from -12°C (10°F) to 16°C (61°F). Temperatures vary considerably through the year.
How much rain does Cornwall get?
Annual rainfall is around 1006 mm (40 in). October is the wettest month with 115 mm (4.5 in), while March is the driest with 57 mm (2.2 in).
Cornwall 3-Day Forecast
Cornwall on the map
Cornwall is highlighted - select any city to see its climate.
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