Rainier, United States offers 1 beach perfect for sunbathing, surfing, swimming, and more. Rainier, Oregon, United States, is known for its scenic views of the Columbia River and proximity to outdoor recreational activities. The best time to travel to Rainier, United States, is during the summer months of July and August, when the average air temperature is around 70°F (21°C) and water temperature in nearby lakes is approximately 65°F (18°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!