If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Mussoorie: The hottest months are usually June and May with an average temp of 71°F, while the coldest months are January and December with an average of 50°F. The rainiest months in Mussoorie are July, August, September, and June, with each month seeing an average of 15 inches of rainfall.