Planning for the weather is a good way to make your trip to São Luís relaxing and enjoyable, especially when you're splurging. The hottest months are usually October and September with an average temp of 81°F, while the coldest months are July and June with an average of 80°F. The rainiest months in São Luís are April, March, February, and May, with each month seeing an average of 21 inches of rainfall.