If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Guamal: The hottest months are usually February and January with an average temp of 71°F, while the coldest months are July and August with an average of 68°F. The rainiest months in Guamal are April, May, June, and July, with each month seeing an average of 12 inches of rainfall.