1. Autumn, the 13th of the twenty-four solar terms and the first solar term of autumn, is celebrated on August 7-9 of the Gregorian calendar every year. At this time, the handles of the seven stars of the Big Dipper point to the southwest, and the sun reaches 135° of yellow longitude. The twenty-four solar terms reflect the changes in the "qi" of the four seasons, and the beginning of autumn is the point at which yang qi gradually withdraws and yin qi gradually grows, gradually changing from yangheng to yinheng. Autumn, also means that precipitation, humidity, etc., is at a turning point in the year, tends to decline or reduce; in nature, everything began to grow from luxuriant tend to mature in the depression.

2, Autumn does not mean that the hot weather is over, Autumn is still in the summer heat period, not yet out of the summer, the second season of autumn (heat) before the summer, the weather is still very hot during early autumn. The so-called "heat in three volts", and "one volt after the fall" said, after the fall there is at least "one volt" of hot weather. In accordance with the "three volts" projection method, "Autumn" this day is often still in the middle of the volts period, that is to say, the summer heat is not over, the real coolness is generally to the White Dew Festival after. The watershed between the heat and the cool is not in the Autumn Festival.

3. Autumn is the season of alternating heat and coolness. The Tube says: "The yin qi of the fall begins to fall, so everything is collected." Entering the fall, the transition from the summer rainy hot and humid to autumn less rainy dry climate. In nature, the yin and yang qi began to change, yang qi gradual collection, yin qi gradual growth, all things with the yang qi sinking and gradually decline. The most obvious change in autumn is that the leaves of grass and trees change from lush green to yellow and begin to fall, while crops begin to ripen. Autumn is one of the ancient "four seasons and eight festivals", the folk have sacrificed to the God of the land, to celebrate the custom of the harvest.