Taking into account the local weather in Ust-Ilimsk can help you maximize your time at the pool during your trip. The hottest months are usually July and June with an average temp of 59°F, while the coldest months are January and December with an average of -1°F. The snowiest months in Ust-Ilimsk are March, February, January, and December, with each month seeing an average of 34 inches of snowfall.