If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Brockville: The hottest months are usually July and August with an average temp of 66°F, while the coldest months are January and February with an average of 25°F. The snowiest months in Brockville are January, December, February, and March, with each month seeing an average of 7 inches of snowfall.