Gumusdere, Turkey offers 3 beaches perfect for sunbathing, surfing, swimming, and more. Gumusdere, Istanbul, Turkey, is known for its beautiful beaches along the Black Sea coast. The best time to travel to Gumusdere, Turkey, is from June to September, when the average air temperature is around 25-30°C (77-86°F) and the water temperature is approximately 22-25°C (72-77°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!