Weather can make or break a roadtrip, so we've gathered some data about year-round temperatures in Green Grass to help you plan yours. The hottest months are usually July and August with an average temp of 71°F, while the coldest months are January and February with an average of 25°F. The snowiest months in Green Grass are December, April, March, and February, with each month seeing an average of 9 inches of snowfall.