If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Darby: The hottest months are usually July and August with an average temp of 63°F, while the coldest months are December and January with an average of 24°F. The snowiest months in Darby are January, December, February, and October, with each month seeing an average of 6 inches of snowfall.