Weather is probably a major factor when you plan your trip to Guiuan, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and June with an average temp of 83°F, while the coldest months are February and January with an average of 81°F. The rainiest months in Guiuan are January, December, November, and July, with each month seeing an average of 17 inches of rainfall.