Kea-Kythnos Regional Unit, Greece offers 1 beach perfect for sunbathing, surfing, swimming, and more. Kea-Kythnos Regional Unit is known for its picturesque Cycladic architecture, the ancient Karthea ruins, and the Loutra hot springs. The best time to travel to the Kea-Kythnos Regional Unit, Greece, is from May to September, with average air temperatures ranging from 24-30°C (75-86°F) and water temperatures around 22-26°C (72-79°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!