Greece Mediterranean. May-June — best time Athens 20-28°C, Santorini 20-25°C. Prices 30-40% lower. July-August — peak Athens 32-40°C. Islands PACKED. Prices double. September — second best. Water warm until October. October-November — low season. Mild 15-22°C. Many islands closed. Winter — Athens culture 8-15°C mild. No visa EU/most.