If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Mu Si: The hottest months are usually April and March with an average temp of 85°F, while the coldest months are January and December with an average of 80°F. The rainiest months in Mu Si are September, August, July, and June, with each month seeing an average of 10 inches of rainfall.