If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Saint Mary’s: The hottest months are usually July and August, with an average temperature of 13°C, while the coldest months are February and January, with an average of -7°C. The snowiest months in Saint Mary’s are March, April, December and January, with each month seeing an average of 83 cm of snowfall.