Derby, United States offers 4 beaches perfect for sunbathing, surfing, swimming, and more. Derby, Vermont, United States, is known for Lake Memphremagog and the Haskell Free Library and Opera House. The best time to travel to Derby, United States, is in late spring (May), when the average air temperature is around 65°F (18°C) and water temperature is approximately 55°F (13°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!