The Autumn Equinox is 16th of traditional 24 solar terms,begins on Sep 23 and ends on Oct 10.After this day,the location of direct sunlight moves to the south, making days shorter and nights longer in the northern hemisphere.

By Autumn Equinox, most of the China's area have entered the cool autumn. When the cold air heading south meets the declining warm and wet air, precipitation is the result. The temperature also drops frequently.