August in Thornhill averages a daily high of 26.6°C with nights around 15.4°C. Expect roughly 9.6 wet days totalling 76.7mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Thornhill is May–September.
Based on TORONTO NORTH YORK, ON CA (4.9km), 1995–2024. 27 years of August data.