The country’s climate is mainly arid and semiarid, except the northern coastal areas and parts of western Iran. The climate is extremely continental with hot and dry summer and very cold winter particularly in inland areas. Apart from the coastal areas, the temperature in Iran is characterized by relatively large annual range, about 22°C to 26°C. The rainy period in most of the country is from November to May followed by dry period between May and October with rare precipitation. The average annual rainfall of the country is about 240 mm with maximum amounts in the Caspian Sea plains, Alborz and Zagros slopes with more than 1,800 and 480 mm, respectively. Iran has climatological diversity with three types of climates: 1) dry and semi-dry climate: large parts of internal lands and southern border of Iran have this climate; 2) Mountainous climate, which itself is subdivided into two categories of cold and moderate mountainous climate; 3) Caspian climate: narrow and small area between Caspian Sea and Alborz Mountain Belt with 600-2000 mm annual rain.