If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Cha-am: The hottest months are usually April and May, with an average temperature of 29°C, while the coldest months are January and December, with an average of 26°C. The rainiest months in Cha-am are September, October, July and August, with each month seeing an average of 205 mm of rainfall.