May in Irkutsk averages a daily high of 18.1°C with nights around 3.7°C. Expect roughly 9.8 wet days totalling 37.2mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Irkutsk is May–August.
Based on IRKUTSK, RS (5.2km), 1995–2024. 25 years of May data.