Weather will likely play an important role when you plan your trip to Gasan, and keep in mind that cheaper options are usually available when the weather isn't as good. 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.