There's nothing like an all-inclusive holiday in Santa María Huatulco to revive you, especially when you know what kind of weather to expect. Here's some information to help you choose when to book: The hottest months are usually April and March, with an average temperature of 26°C, while the coldest months are January and February, with an average of 25°C. February and December are the driest months, while September and June are the rainiest months.