Xi'an has a warm temperate semi-humid continental monsoon climate, exhibiting four distinct seasons and moderate precipitation. The winter of Xi'an is chilly and foggy, with light winds and little rain and snow. Spring is warm, dry, windy, and volatile. Summer is hot, rainy, often associated with thunderstorms and heavy winds, and drought is prominent in midsummer. It is cool in autumn with apparent drop in temperature. The annual temperature is about 15℃. The average temperature of the coolest month (January) is around 0℃, while that of the warmest month (July) is 26℃. The annual precipitation is 500~750 mm, which mainly occurs in summer and autumn. Xi'an has 1,500 hours of sunshine and 208~230 days free of frost per year. Northeasterly wind is the most frequent wind direction in a year.