Plateau of Iran enjoys a relatively dry climate. Iran is situated in the global arid belt Alborz and Zagros mountain chains trap the humidity and air currents of the Caspian Sea and Mediterranean preventing their penetration to the inner parts. Due to being located between 25 and 40 degree latitude and also existence of height, enjoys considerable changeable climate. The average annual temperature increases from northwest to southeast of the country and varies from 10 degree Centigrade in Azarbayjan to 25-30 degree Centigrade in the south and southeast. The northern and southern shores of Iran, in different seasons, have divers climate compared with central and mountainous regions. The average annual temperature of Bandar Abbas in the south of Iran in January is 18.5 degree Centigrade. Difference of average annual rainfall is also very high in different parts of the country. The amplitude of these changes varies from 2000 mm. in Gilan to less than 100 mm. in central parts of Iran. Average annual precipitation in Iran is 275 mm.
Iran enjoys a considerable climate diversity, which is subjected to various seasons in different parts of the country, in a way that is some areas, the coldness of winter and the warmth of summer can be seen simultaneously. Thus the weather in Iran must be Judged regionally.
In January and February, there are three climate zones in Iran. Shores of the Caspian Sea having mild and relatively cold weather, central parts with winter weather, and southern parts that enjoy moderate and pleasant weather. The whole Iran enjoys a pleasant weather in spring, specially in June. But the weather in southern parts grow very hot unexpectedly. The climate condition of the country becomes complicated in summers. Due to high humidity, the weather of the coastal parts of the Caspian Sea changes in summers. During the days it is hot, but it is relatively cool at nights. In southern coastlines of Iran, the days are very hot and the nights relatively warm with very high humidity, which is intolerable by non-native.
The cities of Shiraz, Isfahan, Mashhad, Tehran and Tabriz, which are the main tourism centers of Iran, enjoy different climate. Shiraz with four months of warmth is in the first place and Tabriz with only one month of warmth is in the last place. Azarbayjan, Kurdistan, Hamedan, and Khorasan province are famous as cool places in the summer.
Briefly, entire north of the country, especially countryside of Alborz slopes like Noor valley, Kelardasht, and Katalem, as well as Azarbayjan, Khorasan and central regions of Zagross mountains-between Tooyserkan and Golpayegan are very suitable locations for spending of week-ends and holidays by domestic as well as foreign tourists in summers. Tourists may use the southern region of Iran, regarding their different parts, 5-6 months of the year especially in winters.
Those foreign tourists, who go to the southern coasts of Iran in winters, face a very pleasant weather; while at the same time the cities of Isfahan and Fars provinces are rainy and snowy with a very cold weather. In summers, the weather in the most parts of the country is warm but not intolerable. Spring and autumn, especially Nowrooz holidays (Iranian New Year beginning from March 21st ) are suitable time for touring all around the country.