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As it is said in the ancient book,The Detailed Records of the Spring and Autumn Period (770-476BC), "It is on the Autumn Equinox day that the Yin and Yang are in a balance of power. Thus the day and night are of equal length, and so are the cold and hot weather."

Since the Autumn Equinox, most of the areas in China have entered the cool autumn. When the cold air southward meets the declining warm and wet air, precipitation is the result. The temperature also drops frequently.