Ottawa Weather in August
In August, Ottawa averages a high of 25°C (78°F) and a low of 14°C (58°F), from 55 years of daily records (1971–2026).
25°C
Average high
78°F
14°C
Average low
58°F
37°C
Record high
99°F · August 9, 2001
3°C
Record low
37°F · August 31, 1976
What August Is Like in Ottawa
- The coldest August reading, 3°C (37°F) on August 31, 1976, has not been matched in 50 years.
- A typical August brings 3.3 days above 30°C (86°F).
- August in Ottawa has become 0.7°C (1.3°F) warmer on average: the 2012–2026 average against 1970–1989.
- The warmest August in the record was 2021; the coldest was 1982.
At least 1 mm of rain falls on 28% of August days, and the month averages 90 mm in total.
Warmest: 2001 (28.6°C)Latest: 2026 (24.8°C)10-year averageLong-run average (25.3°C)
Look Up a Day in August
See the weather in Ottawa on any August date, year by year.
Source: NOAA GHCN-Daily, Ottawa Cda (1971–2023); Ottawa Cda Rcs (2000–2026). Averages cover 1971–2026. How we compute this