If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Montmagny: The hottest months are usually July and August with an average temp of 60°F, while the coldest months are January and February with an average of 16°F. The snowiest months in Montmagny are January, February, March, and November, with each month seeing an average of 47 inches of snowfall.