If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Irkutsk: The hottest months are usually July and June, with an average temperature of 15°C, while the coldest months are January and February, with an average of -15°C. The snowiest months in Irkutsk are April, January, December and February, with each month seeing an average of 31 cm of snowfall.