May in Calgary averages a daily high of 16.7°C with nights around 3.3°C. Expect roughly 8.9 wet days totalling 44.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Calgary is June–September.
Based on CALGARY INTERNATIONAL CS, AB CA (8.8km), 1995–2024. 23 years of May data.