If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Itanhaem: The hottest months are usually February and January with an average temp of 77°F, while the coldest months are July and August with an average of 67°F. The rainiest months in Itanhaem are January, February, March, and December, with each month seeing an average of 11 inches of rainfall.