If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Sen Monorom: The hottest months are usually April and March with an average temp of 79°F, while the coldest months are January and February with an average of 73°F. The rainiest months in Sen Monorom are September, July, August, and October, with each month seeing an average of 10 inches of rainfall.