If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Terrebonne: The hottest months are usually July and August with an average temp of 65°F, while the coldest months are January and February with an average of 21°F. The snowiest months in Terrebonne are February, January, December, and March, with each month seeing an average of 35 inches of snowfall.