Sennan, Japan offers 1 beach perfect for sunbathing, surfing, swimming, and more. Sennan is known for the Rinku Premium Outlets and the Sennan Long Park. The best time to travel to Sennan, Japan, is in late spring (May), when the average air temperature is around 20°C (68°F) and the water temperature is approximately 18°C (64°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!