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.

Climate in Tehran

Three factors play an effective role in the climate of Tehran: Alborz mountains, the western humid currents, and the latitude. As a matter of fact, Alborz mountains make the weather in Tehran moderate. In northern Tehran, the weather is moderate and mountainous, and in plains it is semi-arid. A major part of precipitation takes place in winter. Average annual rainfall stands at 200 millimeters.
The cold season usually begins in December, but in the mountainous regions, it begins earlier. The cold season lasts 3 or 4 months. In mid-March, the weather grows warm. In late April, the weather begins to grow warm at a faster pace, so that in mid-May, it is rather hot.