Lebanon, United States offers 3 beaches perfect for sunbathing, surfing, swimming, and more. Lebanon, New Jersey, United States, is known for Round Valley Reservoir and its outdoor recreational activities. The best time to travel to Lebanon, United States, is during the summer months of June to August, with average air temperatures around 70-80°F and water temperatures in the mid-60s°F. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!