Autumn, is the "twenty-four solar terms" of the thirteenth solar term, but also the beginning of autumn. Doo refers to the southwest, the sun reaches 135 ° yellow longitude, in the annual calendar August 7 or 8 cross section. The word "Li" means "beginning", and the word "Autumn" means the ripening of the grain. Changes in the entire natural world are gradual processes. Autumn is the turning point when yang qi gradually closes and yin qi gradually grows, gradually changing from yangheng to yinheng. In the natural world, everything begins to mature from luxuriant growth to maturity.

Autumn is the third hottest of the twenty-four solar terms after the summer heat. In the order of the solar terms, the summer heat comes after the autumn, and the second solar term in the fall, "the summer heat" (the end of the summer) is only out of the summer. Twenty-four seasons have "three summer" (small summer, summer, heat), "three summer" in the middle of the "autumn", after the fall is the heat (the end of the summer). The "three summers" and the "three volts" both represent hot weather, and the "three volts day" involves the four solar terms of Xiaoshu, Daoshu, Liqiu, and Shiushu. Among the 24 solar terms, the summer days are longer.

Autumn means that precipitation and humidity are at a turning point in the year, tending to fall or decrease. Starting from the beginning of autumn, yang qi gradually collects, and all things are inwardly convergent. Autumn and spring, summer, winter and known as the "four Li", is also one of the ancient "four times eight sections". Autumn is the season of grain ripening and harvesting. In ancient times, there were folk customs to celebrate the harvest. There are also customs such as "sticking autumn fat" and "biting autumn".

Autumn marks the official start of the Mengqiu season, which is second only to the summer, the third heat of the summer, the weather is still very hot after the autumn, Chinese medicine will be the autumn to the autumn equinox before the period called "long summer". After the autumn, in nature, the yin and yang qi began to change, everything with the yang qi sinking and thus began to grow from luxuriant growth to maturity. In the ancient agricultural society of China, the beginning of the fall has an important significance, folk in the beginning of the fall sacrifice to the land, to celebrate the harvest.

Entering the fall season means that rainfall, humidity, etc., is at a turning point in the year and tends to decline or decrease. Seasonal transition, rainfall, dryness and humidity, etc. in the southern region of the change is obvious; northern regions, the change is obvious temperature. After entering the fall, in nature, the yin and yang qi began to shift, everything began to grow from luxuriant tend to depression and maturity, the climate began to be hot and humid from the summer rainfall to the fall of the transition to a dry climate with little rain. Autumn indicates the beginning of the seasonal transition, but does not mean that the temperature will immediately drop. The "three volts" in the last volts is still after the autumn festival.