Iran has a hot, dry climate characterized by long, hot, dry summers and short, cool winters. Iran climate is influenced by Iran's location between the subtropical aridity of the Arabian Desert areas and the subtropical humidity of the eastern Mediterranean area. January is the coldest month, with temperatures from 5°C to 10°C, and August is the hottest month at 20°C to 30°C or more.
In most of the areas, summers are warm to hot with virtually continuous sunshine, but high humidity on the southern coastal areas of the Persian Gulf. Daily Temperatures can be very hot; on some days temperatures can reach easily 40°C or more, especially along the Persian Gulf and Oman Sea which causes a danger of heat exhaustion.
About 70 percent of the average rainfall in the country falls between November and March; June through August are often rainless. Rainfall varies from season to season and from year to year. Precipitation is sometimes concentrated in local, but violent storms, causing erosion and local flooding, especially in the winter months. A small area along the Caspian coast has a very different climate; here rainfall is heaviest from late summer to mid winter but falls in general throughout the year.
Lightweight Cotton clothes are advised in the summer, with a sweater for cooler evenings, especially in the inland areas. Waterproof medium wear is recommended for the winter, and warmer clothing for the mountainous areas of northern Iran.
Climate of Iran can be divided in at least four different climate zones. The Climate of the Western and southwestern areas can be classified as BWh Climate; a hot, dry desert climate with annual average temperatures above 18°C. a small zone between the Persian Gulf the Turkish Border in the mid of Iran can be classified as BSh climate, a hot, dry Climate with the annual average Temperature above 18°C. The eastern and northern areas of Iran have a Csa Climate; a mild, semi-humid climate with dry summers, mild winters and the warmest month above 22°C. Finally, the mountainous regions of northern Iran can be classified as Dsa Climate, a cold snow Climate with dry summers and wet winters with the warmest month over 22°C and the coldest month below -3°C.