If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Rai Som: The hottest months are usually April and May, with an average temperature of 30°C, while the coldest months are December and January, with an average of 27°C. The rainiest months in Rai Som are September, October, May and July, with each month seeing an average of 201 mm of rainfall.