Despite the general dry trend for a sizable part of the country, for the rest the climate is ‎surprisingly varied. In the northwest, winters are cold with heavy snowfall and subfreezing ‎temperatures during December and January. Spring and fall are relatively mild, while summers are ‎dry and hot. In the south, winters are mild and the summers are very hot, having average daily ‎temperatures in July exceeding 38° C (100° F). On the Khuzestan plain, summer heat is ‎accompanied by high humidity.‎

Most of the annual precipitation falls from October through April. In most of the country, yearly ‎precipitation averages 25 centimeters or less. The major exceptions are the higher mountain ‎valleys of the Zagros and the Caspian coastal plain, where precipitation averages at least 50 ‎centimeters annually. In the western part of the Caspian, rainfall exceeds 100 centimeters ‎annually and is distributed relatively evenly throughout the year. This contrasts with some basins ‎of the Central Plateau that receive ten centimeters or less of precipitation annually.‎