The beginning of autumn is the thirteenth solar term of the “Twenty-Four Solar Terms” and the first solar term in autumn. Dou refers to the southwest, the sun reaches 135° ecliptic longitude, and it meets on August 7 or 8 of the Gregorian calendar every year. The change of the whole nature is a gradual process. The beginning of autumn is a turning point when the yang qi gradually shrinks, the yin qi gradually grows, and the yang qi gradually changes into the yin qi. In nature, everything begins to grow from flourishing to bleak and mature.

The beginning of autumn does not mean the end of the hot weather. The beginning of autumn is still in the hot period, and the summer has not yet come out. The second solar term in autumn (the end of summer) is the summer, and the weather is still very hot during the early autumn. The so-called “heat is in the three volts”, and there is a saying of “one volt after autumn”, and there will be at least “one volt” of extremely hot weather after the beginning of autumn. According to the calculation method of “San Fu”, the “Liqiu” day is often still in the middle period, that is to say, the hot summer is not over, and the real coolness usually comes after the Bailu solar term. The hot and cool watershed is not the beginning of autumn.

After entering autumn, it transitions from the rainy, humid and hot summer to the drier and dry climate in the autumn. In nature, the yin and yang qi begins to change, and all things gradually decline as the yang qi sinks. The most obvious change in autumn is when the foliage goes from lush green to yellow and begins to drop leaves and the crops begin to mature. The beginning of autumn is one of the “four seasons and eight festivals” in ancient times. There is a custom among the people to worship the gods of the land and celebrate the harvest. There are also customs such as “sticking autumn fat” and “biting autumn”.