If you're hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Bagan: The hottest months are usually April and May with an average temp of 88°F, while the coldest months are January and December with an average of 75°F. The rainiest months in Bagan are September, August, October, and July, with each month seeing an average of 7 inches of rainfall.