You might spend a lot of your vacation inside, but if you're planning to venture beyond the casino, taking a look at local weather data can help you. The hottest months are usually March and April with an average temp of 84°F, while the coldest months are December and January with an average of 80°F. The rainiest months in San Miguel are October, June, September, and August, with each month seeing an average of 13 inches of rainfall.