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Sarnia (ON) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Sarnia.
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Climate overview of Sarnia
The climate in Sarnia, Ontario, Canada, is marked by large temperature swings across the seasons, ranging from 27°C (81°F) in July to 0°C (32°F) in January.
Sarnia sees a moderate amount of rain/snowfall, totalling around 970 mm (38 in) per year. It experiences warm summers and very cold winters, creating some seasonal variation.
Sarnia Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Sarnia - and find the best time to visit.
Monthly Temperature in Sarnia
In Sarnia, 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 0°C (32°F) during cooler months like January.
At night, you can expect temperatures ranging from 19°C (66°F) in July to around -7°C (19°F) during January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Sarnia
On average, Sarnia receives a reasonable amount of rain/snowfall, with an annual precipitation of 970 mm (38 in). Year-round, Sarnia has a balanced climate with minimal variation in precipitation. The difference between the wettest month, June, with 97 mm (3.8 in), and the driest month, March, with 66 mm (2.6 in), is minimal. For more details, please visit our Sarnia 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 Sarnia
The most comfortable overall weather for exploring Sarnia is usually found in June, July, August and September. Conditions are generally least comfortable 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
cold
Feb
cold
Mar
cold
Apr
mixed
May
very good
Jun
excellent
Jul
excellent
Aug
excellent
Sep
excellent
Oct
good
Nov
cold
Dec
cold
- Best overall: June, July, August and September
- Warmest weather: July and August
- Seasonal pattern: Warm summers and very cold winters
- Coldest conditions: January, with freezing nights around -7°C (19°F).
Frequently asked questions about the climate in Sarnia
What is the best time to visit Sarnia?
June, July, August and September typically offer the most optimal weather in Sarnia. In contrast, January, February, March, November and December tend to have less optimal conditions. Sarnia has warm summers and very cold winters.
What temperatures can I expect in Sarnia?
Daytime highs range from 0°C (32°F) in January to 27°C (81°F) in July. Nighttime lows range from -7°C (19°F) to 19°C (66°F). Temperatures vary considerably through the year.
How much rain does Sarnia get?
Annual rainfall is around 970 mm (38 in). June is the wettest month with 97 mm (3.8 in), while March is the driest with 66 mm (2.6 in).
Sarnia 3-Day Forecast
Sarnia on the map
Sarnia is highlighted - select any city to see its climate.
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Toronto
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