Why is the climate in Beijing so dry?

Beijing's climate is a typical warm temperate semi-humid continental monsoon climate, with hot and rainy summer, cold and dry winter and short spring and autumn. Annual average temperature 10~ 12 degrees Celsius. 1October 65438+-7~-4 degrees Celsius, July 25~26 degrees Celsius. The extreme minimum is -27.4 degrees Celsius, and the extreme maximum is above 42 degrees Celsius. The frost-free period of the whole year is 180~200 days, which is shorter in the western mountainous area. The annual average rainfall is more than 600 mm, which is one of the most rainy areas in North China. The windward slope in front of the mountain can reach more than 700 mm, and the seasonal distribution of precipitation is very uneven. 80% of the annual precipitation is concentrated in June, July and August in summer, and there are often heavy rains in July and August.