If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Saint Mary’s: The hottest months are usually July and August with an average temp of 56°F, while the coldest months are February and January with an average of 20°F. The snowiest months in Saint Mary’s are March, April, December, and January, with each month seeing an average of 33 inches of snowfall.