The summer season runs from Memorial Day through Labor Day, and that is when the island is busiest, hottest, and at its most expensive. Water temperatures climb into the low 80s Fahrenheit, the rental houses are full, and you will need to book months ahead for a beachfront cottage. Hurricane season runs from June through November, but the worst storms tend to come in late August and September.
Shoulder seasons — May, late September, and October — are the real sweet spot. The water is still swimmable, the crowds have thinned, restaurants are easier to get into, and rates drop. Winter is quiet, mild by northern standards, and lovely for long beach walks with no one else in sight, but many of the restaurants and rental businesses close down. If you want to see sea turtle nests hatching, aim for July or August and contact the turtle patrol in advance.