If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Belle Fourche: The hottest months are usually July and August with an average temp of 69°F, while the coldest months are February and January with an average of 27°F. The snowiest months in Belle Fourche are April, December, March, and February, with each month seeing an average of 11 inches of snowfall.