September in Montréal averages a daily high of 21.5°C with nights around 12.7°C. Expect roughly 9.9 wet days totalling 87.9mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Montréal is May–September.
Based on MCTAVISH, QC CA (1km), 1995–2024. 27 years of September data.