You might spend a lot of your vacation inside, but if you're planning to venture beyond the casino, looking at local weather trends is a good idea. The hottest months are usually May and June with an average temp of 83°F, while the coldest months are February and January with an average of 79°F. The rainiest months in Gasan are December, January, September, and November, with each month seeing an average of 19 inches of rainfall.