Castro Marim, Portugal offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Castro Marim is known for its beautiful beaches and historical attractions in the Algarve region. The best time to travel to Castro Marim, Portugal, is from May to September, when the average air temperature ranges from 25°C to 30°C (77°F to 86°F) and the water temperature is around 20°C to 24°C (68°F to 75°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!