August in Ottawa averages a daily high of 25.9°C with nights around 14.9°C. Expect roughly 10.8 wet days totalling 89.1mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Ottawa is May–September.
Based on OTTAWA CDA, ON CA (3.4km), 1995–2024. 29 years of August data.