Planning for the weather is a good way to make your trip to Isla San Jose relaxing and enjoyable, especially when you’re splurging. The hottest months are usually March and April, with an average temperature of 28°C, while the coldest months are February and January, with an average of 27°C. The rainiest months in Isla San Jose are July, August, May and June, with each month seeing an average of 498 mm of rainfall.