Weather can make or break a roadtrip, so we've gathered some data about year-round temperatures in Terreton to help you plan yours. 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 Terreton are March, January, February, and December, with each month seeing an average of 8 inches of snowfall.