Hamadan province lies in a temperate mountainous region to the east of Zagros. The vast plains of the north and northeast of the province are influenced by strong winds, that almost last throughout the year.
It is characterized by fairly long, cold winters (between 120 and 140 days of frost) and mild summers. The weather becomes gradually milder as we move from the northern highlands and plateaus towards the south. The northern valleys and vast plains are also exposed to northern and northwesterly winds in the winter, blowing with an average speed of 4 m per second. They are generally humid and bring about rainfall (Razmārā, Farhang V, p. 480; Faraji, p. 1290). The west-east winds blow in the autumn and the local winds (like the blind wind of Asadābād) are brought about by difference in air pressure due to differences in altitudes.
The various air currents of this region are: the north and north west winds of the spring and winter seasons, which are usually humid and bring rainfall. The west-east air currents that blow in the autumn, and the local winds that develop due to difference in air-pressure between the elevated areas and the plains, like the blind wind of the Asad Abad region.
The temperature varies between minus 32 Celsius in winter to 39 Celsius in summer, with average temperatures between minus 4 (in December) and 25 (in July). Mountain tops are snow-covered from six to eight months of the year.
Hamadan is in the vicinity of the Alvand mountains and has a dry summer continental climate (Köppen climate classification
Dsa), in transition with a cold semi-arid climate (Köppen climate classification BSk), with snowy winters. In fact, it is one of the coldest cities in Iran. The temperature may drop below −30 °C (−22 °F) on the coldest days. Heavy snowfall is common during winter and this can persist for periods of up to two months. During the short summer, the weather is mild, pleasant, and mostly sunny.
Precipitation has fluctuated between 280 and 420 mm in recent years, with an average of 315 mm. This has enabled Hamadān to sustain a relatively prosperous agriculture. The rainfall is almost equally divided into two periods of six months from November until April. There is practically no rain from June to September