Characteristics of the autumnal equinox: 1. The position of direct sunlight continues to move from the equator to the southern hemisphere. The daytime is shorter than the night in the northern hemisphere until the winter solstice reaches the shortest day. 2. The temperature difference between day and night will gradually increase, and the amplitude will be higher than 10℃. 3. The temperature is dropping day by day, getting colder day by day, and gradually entering the late autumn season. The opposite is true in the Southern Hemisphere.

The autumnal equinox is the sixteenth solar term among the twenty-four solar terms. It usually falls between September 22nd and 24th in the Gregorian calendar every year. During the autumnal equinox, most parts of our country have entered a cool autumn. The cold air coming from the south meets the gradually attenuating warm and humid air, resulting in repeated precipitation and temperature drops again and again.

According to the lunar calendar, "Beginning of Autumn" is the beginning of autumn and "Frost Descent" is the end of autumn. The "Autumnal Equinox" is exactly half of the 90 days from Beginning of Autumn to Frost Descent.

At the autumnal equinox, my country’s Yangtze River Basin and the vast areas north of it have entered autumn, and the daily average temperature has dropped below 22°C. The cold air mass in the north has begun to have a certain influence. The rainy season has just ended in most areas. There is a cool breeze, blue sky, sunny wind and clear autumn air.