Iran is one of the rare four-season countries with variety of changing climate.
In the North West (Tabriz, Orumieh, Ardabil, Zanjan, Tehran), winters are cold with heavy snowfall and subfreezing temperatures especially during December and January.
In the south and center; weather is sunny most of the time, except some rainfalls in winter and spring.

 

 

In the Western part of the Caspian Sea (Rasht, Sari, Golestan), rainfall exceeds 100 centimeters annually and is distributed relatively evenly throughout the year.
On the other hand in the South (Bandar Abbas, Boushehr, Ahvaz) winters are mild and the summers are almost very hot, average daily temperatures in July exceeding 38° C. The days are extremely hot and the nights are mild from June to October.
In most of the country's East & West (Shiraz, Isfahan), yearly precipitation averages of weather are 25 centimeters or less. Also springs and falls are relatively mild with pleasant weather in March and April.
In general, it has an arid climate in which most of the relatively scant annual precipitation falls. But, the major exceptions are the higher mountain valleys of the Zagros and the Caspian Sea coastal plain, where precipitation averages at least 50 centimeters annually. Snow falls heavily on the mountain peaks and is the principal source of water for irrigation in spring and early summer. The Caspian littoral is warm and humid throughout the year. Here the seasons change abruptly; by the Persian New Year, the first day of spring, orchards are in bloom and wild flowers abound.
The temperature difference between different points in Iran during the summer and winter is 100 that in the book of Mr.Afshin Bakhtiar has been introduce as one of the cryptic numbers of Iranian nature. In fact, the secret of Iran's varied nature is encoded in seven 'magic' numbers, that 100 is one of them:
100: The temperature difference between different points in Iran during the summer and winter. In Hamadan, for example, the temperature drops by at least 2°C if one climbs just 200 meters up Mount Alvand. Similarly, in AbarKouh, a few kilometers in to the desert the temperature will undoubtedly climb more than a few degrees. If we assume that the temperature drops by about 1°C for every 100 meters elevation, the question of what constitutes the" correct" temperature becomes rather more difficult to answer. How low is the temperature at 4000 meters, or on top of Mount Damavand (5671 m), for that matter? At the other ends of the scale, my esteemed mentor; Dr Parviz Kardavani believes that the warmest point on the planet is not to be found, as claimed elsewhere. In Arizona, Arabia or the deserts of Libya but instead in the Kavir-e- Lut in Iran, where temperatures in excess of 600 C have been reported. Accordingly, assuming the temperature atop the highest peaks in Iran reaches at least 400 C below zero and that in the Kavir-e Lut reaches 60°C, the temperature difference thus obtained equals 100°e, a figure of much significance.
600: The highest point in the Iranian Plateau, Mount Damavand. , Stands 5671 meters above and its lowest point, in the vicinity of the Caspian Sea, lies27 meters below sea level. Simple arithmetic indicates, therefore, that the elevation range in the Iranian plateau equals approximately 6000 meters.