If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Fosston: 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 15°F. The snowiest months in Fosston are March, February, December, and January, with each month seeing an average of 6 inches of snowfall.