July in Thornhill averages a daily high of 27.7°C with nights around 16.2°C. Expect roughly 10.6 wet days totalling 83.9mm. 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 July data.