October in Sarnia averages a daily high of 16.4°C with nights around 7.6°C. Expect roughly 12.6 wet days totalling 79.8mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Sarnia is May–September.
Based on PORT HURON, MI US (1.3km), 1995–2024. 29 years of October data.