If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Marysville: The hottest months are usually July and August with an average temp of 68°F, while the coldest months are February and January with an average of 29°F. The snowiest months in Marysville are January, March, February, and December, with each month seeing an average of 6 inches of snowfall.