T he plain region of Xi’an City has a warm temperate semi-humid continental monsoonal climate with 4 distinct seasons having obvious differences in temperature and humidity. The winter is cold with small wind, more fog, less sleet; the spring is warm and dry with more wind and changeable climate; the summer is hot with more rain, highlighted summer drought, more thunderstorm and strong wind; the autumn is nice and cool with sharp temperature drop and typical autumn rain. The annual average temperature is 13.0?C~ 13.7?C, the average temperature of January, the coldest month, is -1.2?C~ 0.0?C, the average temperature of July, the hottest month, is 26.3?C~ 26.6?C, the annual extreme low temperature is -21.2?C (Lantian, December 28, 1991), the annual extreme high temperature is 43.4?C (Changan, June 19, 1966). The annual precipitation is 522.4~ 719.5 mm, increasing progressively from north to south. The two obvious precipitation peak months are July and September. The annual sunshine duration is 1646.1~ 2114.9 hours. The annual prevailing wind direction varies from place to place: northeaster in downtown Xi’an, west wind in Zhouzhi and Huxian, east wind and northeaster in Gaoling and Lintong, southeaster in Chang’an, and northwester in Lantian. The meteorological disasters include drought, continuous rain, rainstorm, flood, urban inland inundation, hail, gale, dry-hot wind, hyperthermia, thunderbolt, dust storm, heavy fog, haze, cold wave, frozen injury.