Planning for the weather is an important factor for making your trip to San Agustinillo a success, especially when you're splurging. The hottest months are usually April and March with an average temp of 78°F, while the coldest months are January and February with an average of 76°F. The rainiest months in San Agustinillo are September, June, August, and October, with each month seeing an average of 20 inches of rainfall.