Weather is probably a major factor when you plan your trip to Cha-am, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually April and May with an average temp of 84°F, while the coldest months are January and December with an average of 79°F. The rainiest months in Cha-am are September, October, July, and August, with each month seeing an average of 8 inches of rainfall.