Deer Isle, United States offers 5 beaches perfect for sunbathing, surfing, swimming, and more. Deer Isle is known for the Haystack Mountain School of Crafts and the scenic Deer Isle Bridge. The best time to travel to Deer Isle, United States, is during the summer months of June to August, when the average air temperature is around 70°F (21°C) and the water temperature is approximately 60°F (16°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!