If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Garapan: The hottest months are usually July and August with an average temp of 83°F, while the coldest months are February and March with an average of 81°F. The rainiest months in Garapan are August, October, September, and July, with each month seeing an average of 15 inches of rainfall.