If you're hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Sukhothai: The hottest months are usually April and March with an average temp of 86°F, while the coldest months are December and January with an average of 78°F. The rainiest months in Sukhothai are August, September, July, and May, with each month seeing an average of 10 inches of rainfall.