Kos weather: Because of its mild Mediterranean climate, the island of Kos has a lot of sunny days throughout the year. The temperature of the water remains quite high for many months and allows the visitors to enjoy it even in the low season. Kos weather is characterized by the endless sunshine which is very attractive during the summer months. The climate of Kos is quite pleasant with mild temperatures that range from 13°C during the winter to 30°C in the summer. Rain is quite rare in Kos, especially in the summer.