If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Rexburg: The hottest months are usually July and August with an average temp of 66°F, while the coldest months are January and December with an average of 24°F. The snowiest months in Rexburg are January, February, March, and December, with each month seeing an average of 12 inches of snowfall.