Mount Desert, United States offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Mount Desert, Maine, United States, is known for Acadia National Park. The best time to travel to Mount Desert, United States, is from June to September, with average air temperatures ranging from 60-75°F and water temperatures around 55-65°F. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!