May in Waterloo averages a daily high of 18.9°C with nights around 7°C. Expect roughly 9.7 wet days totalling 72.8mm. 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. 21 years of May data.