If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Middleton: The hottest months are usually July and August with an average temp of 62°F, while the coldest months are February and January with an average of 29°F. The snowiest months in Middleton are February, January, December, and April, with each month seeing an average of 18 inches of snowfall.