Seaside, United States offers 12 beaches perfect for sunbathing, surfing, swimming, and more. Seaside is known for its historic Seaside Promenade and the Seaside Aquarium. The best time to travel to Seaside, United States, is from June to August, when the average air temperature is around 70-75°F and the water temperature is approximately 60-65°F. Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!