Siuntio, Finland offers 2 beaches perfect for sunbathing, surfing, swimming, and more. Siuntio is known for its historical Siuntio Church and the Sjundby Manor. The best time to travel to Siuntio, Finland, is during the summer months of June to August, when the average air temperature is around 15-20°C (59-68°F) and the water temperature is approximately 15-18°C (59-64°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!