Taking into account the local weather in Roscommon is an important factor for planning your visit, especially if you plan to spend your trip poolside. The hottest months are usually July and August with an average temp of 65°F, while the coldest months are February and January with an average of 24°F. The snowiest months in Roscommon are January, February, December, and March, with each month seeing an average of 8 inches of snowfall.