If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Chachoengsao: The hottest months are usually April and May with an average temp of 85°F, while the coldest months are December and January with an average of 81°F. The rainiest months in Chachoengsao are September, October, July, and August, with each month seeing an average of 8 inches of rainfall.