If you're looking forward to lots of outings with your partner, check out these details about year-round temperatures in Chiang Khan: The hottest months are usually April and March with an average temp of 80°F, while the coldest months are January and December with an average of 72°F. The rainiest months in Chiang Khan are August, September, July, and June, with each month seeing an average of 10 inches of rainfall.