October in Thornhill averages a daily high of 14.9°C with nights around 5.6°C. Expect roughly 12.6 wet days totalling 72.9mm. Generally workable, with some weather to plan around.
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 October data.