If you're hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Ko Mook: The hottest months are usually March and February with an average temp of 83°F, while the coldest months are January and February with an average of 82°F. The rainiest months in Ko Mook are September, October, August, and July, with each month seeing an average of 14 inches of rainfall.