If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Prambanan: The hottest months are usually October and September with an average temp of 77°F, while the coldest months are August and September with an average of 77°F. The rainiest months in Prambanan are February, January, March, and December, with each month seeing an average of 16 inches of rainfall.