Petersburg, United States offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Petersburg, Indiana, United States, is not particularly known for travel and beach tourism. The best time to travel to Petersburg, United States, is during the summer months of June to August, when the average air temperature is around 60-70°F (15-21°C) and the water temperature is approximately 50-60°F (10-15°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!