Exo Gialos Thiras, Greece offers 1 beach perfect for sunbathing, surfing, swimming, and more. Exo Gialos Thiras, South Aegean, Greece, is known for its picturesque black sand beach and proximity to the stunning caldera views of Santorini. The best time to travel to Exo Gialos Thiras, Greece, is from late May to early October, with average air temperatures around 75°F (24°C) and water temperatures around 73°F (23°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!