Grantsville, United States offers 1 beach perfect for sunbathing, surfing, swimming, and more. Grantsville is known for the Casselman River Bridge State Park and the historic Penn Alps Restaurant and Craft Shop. The best time to travel to Grantsville, United States, is in late spring (May to June) when the average air temperature is around 60-70°F, and water temperatures in nearby lakes are typically cooler, around 50-60°F. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!