December in Calgary averages a daily high of -0.5°C with nights around -12.2°C. Expect roughly 7.1 wet days totalling 12.5mm. A hard month to visit for comfort alone.
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 December data.