Omis, Croatia offers 7 beaches perfect for sunbathing, surfing, swimming, and more. Omis is known for the Cetina River, the Omis Riviera, and the historic Mirabella Fortress. The best time to travel to Omis, Croatia, is from June to September, when the average air temperature is around 75°F (24°C) and the sea temperature is approximately 75°F (24°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!