If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Amatlán: The hottest months are usually April and May with an average temp of 74°F, while the coldest months are January and December with an average of 65°F. The rainiest months in Amatlán are September, August, July, and June, with each month seeing an average of 13 inches of rainfall.