Iran is one of the only countries in the world which has the complete four seasons.In summer, the weather can be cool as well as warm, and in the cold winters, it can be mild.A large part of the country suffers great extremes of heat and cold between summer and winter and rainfall is mainly confined to winter and spring. Summers are warm to hot with virtually continuous sunshine, with high humidity on the southern coasts. Very high temperatures can be experienced along the Persian Gulf and Oman Sea with a danger of heat exhaustion. Winter weather is very changeable with some mild, wet spells but also some very cold periods with frost and snow. A small area along the Caspian coast has a very different climate, here rainfall is heaviest from late summer to mid winter but falls throughout the year.