If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in New 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 New Bagan are September, August, October, and July, with each month seeing an average of 7 inches of rainfall.