If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Evanston: The hottest months are usually July and August with an average temp of 62°F, while the coldest months are January and December with an average of 20°F. The snowiest months in Evanston are March, February, April, and January, with each month seeing an average of 12 inches of snowfall.