Ontario (CA) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Ontario.
Climate overview of Ontario
The climate in Ontario, California, United States of America, is marked by large temperature swings across the seasons, ranging from 34°C (93°F) in August to 19°C (66°F) in December.
With around 273 mm (11 in) of annual rainfall, Ontario has a fairly dry climate. However, it has a distinct dry season from March to November, with very warm summers and pleasant winters. The wettest month is December, while June sees the least rain. July is the sunniest month, averaging 12.3 hours of sunshine per day.
Ontario Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Ontario - and find the best time to visit.
Monthly Temperature in Ontario
In Ontario, temperatures differ significantly between summer and winter months. Average daytime temperatures reach a very warm 34°C (93°F) in August. In December, the coolest month of the year, temperatures drop to a pleasant 19°C (66°F).
At night, temperatures range from around 18°C (64°F) in August to 6°C (43°F) in December.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Ontario
Ontario tends toward drier weather patterns, receiving approximately 273 mm (11 in) of rain per year. Ontario can be quite wet during December, receiving approximately 78 mm (3.1 in) of precipitation over 8 rainy days.
In contrast, during the driest month (June), you will experience much drier conditions, with 0.1 mm (0 in) of precipitation spread across 0 rainy days. For more details, please visit our Ontario Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Ontario
Ontario can be enjoyed more throughout the sunniest month of July under a blue sky, with approximately 12.3 hours of sunshine daily. In contrast, the city experiences much darker days in January, with only 6.6 hours of sunlight per day.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Daily hours of sunshine
Best Time to Visit Ontario
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
- Best overall: January, February, March, April, May, October and November
- Warmest weather: July, August and September
- Most sunshine: July and August
- Fewer rainy days: May, June, July, August and September
- Seasonal pattern: A distinct dry season from March to November, with very warm summers and pleasant winters
Frequently asked questions about the climate in Ontario
What is the best time to visit Ontario?
January, February, March, April, May, October and November typically offer the most optimal weather in Ontario. In contrast, August tends to have less optimal conditions. Ontario has a distinct dry season from March to November, with very warm summers and pleasant winters.
What temperatures can I expect in Ontario?
Daytime highs range from 19°C (66°F) in December to 34°C (93°F) in August. Nighttime lows range from 6°C (43°F) to 18°C (64°F). Temperatures vary considerably through the year.
How much rain does Ontario get?
Annual rainfall is around 273 mm (11 in). December is the wettest month with 78 mm (3.1 in), while June is the driest with 0.1 mm (0 in).
How sunny is Ontario?
Ontario receives around 3,279 hours of sunshine per year. July is the sunniest month with 369 hours, while January is the cloudiest with just 198 hours. Overall, Ontario enjoys abundant sunshine.
Ontario 3-Day Forecast
Ontario (CA) 3-Day Forecast
Ontario on the map
Ontario is highlighted - select any city to see its climate.
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