September in Waterloo averages a daily high of 21.7°C with nights around 10.3°C. Expect roughly 9.3 wet days totalling 81.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Waterloo is May–September.
Based on ROSEVILLE, ON CA (13.6km), 1995–2024. 25 years of September data.