Sullivans Island, United States offers 12 beaches perfect for sunbathing, surfing, swimming, and more. Sullivans Island is known for Fort Moultrie and its beautiful beaches. The best time to visit Sullivans Island is from late spring to early fall, with average air temperatures ranging from 70°F to 85°F and water temperatures between 75°F and 80°F. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!