Ottawa Weather in August

The climate in Ottawa during August can be summarized as warm, humid and a little damp.

August is in the summer in Ottawa and is typically the 2nd warmest month of the year. Daytime maximum temperatures average around a muggy 29°C (83°F), whilst at night 17°C (62°F) is normal.

On average August is the 5th wettest month of the year in Ottawa with around 90mm 3.5 inches of rain making it a a little damp time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 9.8 hours of sunshine per day.

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Ottawa in August 2025.