Ustronie Morskie, Poland offers 4 beaches perfect for sunbathing, surfing, swimming, and more. Ustronie Morskie is known for its beautiful Baltic Sea beaches and the historic Church of St. Mary of the Assumption. The best time to travel to Ustronie Morskie, Poland, is during the summer months of June to August, when the average air temperature is around 20-25°C (68-77°F) and the Baltic Sea water temperature is approximately 18-20°C (64-68°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!