Planning for the weather is a good way to make your trip to Isla Grande relaxing and enjoyable, especially when you're splurging. The hottest months are usually May and September with an average temp of 80°F, while the coldest months are January and February with an average of 79°F. The rainiest months in Isla Grande are November, July, August, and October, with each month seeing an average of 14 inches of rainfall.