December in Irkutsk averages a daily high of -10.7°C with nights around -18.9°C. Expect roughly 12.6 wet days totalling 19.1mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Irkutsk is May–August.
Based on IRKUTSK, RS (5.2km), 1995–2024. 24 years of December data.