If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Yelm: The hottest months are usually August and July with an average temp of 62°F, while the coldest months are February and December with an average of 40°F. The rainiest months in Yelm are November, December, January, and March, with each month seeing an average of 8 inches of rainfall.