Lamar, United States offers 1 beach perfect for sunbathing, surfing, swimming, and more. Lamar, Texas, United States, is known for Goose Island State Park and the historic Big Tree. The best time to travel to Lamar, United States, is in late spring (May), when the average air temperature is around 70°F (21°C) and water temperature is not applicable as it is a landlocked area. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!