Qushu means "going out of heat", which means leaving the heat.

Sushu is the fourteenth solar term of the twenty-four solar terms and the second solar term in autumn. Dou Zhi Wu (southwest); the sun's yellow longitude reaches 150°; the festival is held between August 22 and 24 of the Gregorian calendar every year. It's the end of the summer heat, and the "last heat" of the "three heats" of high-temperature and scorching weather has arrived, which means that the hot and unbearable weather has come to an end.

After the end of summer, the direct sun point continues to move southward, solar radiation weakens, and the subtropical high pressure also retreats southward, and the heat gradually subsides. Thunderstorm activity is also less active than in hot summer, and the general trend of heavy rains across the country has weakened. There are many folk activities during summer heat, such as eating ducks, setting off river lanterns, holding a fishing festival, making herbal tea, worshiping the Earth God, etc.

The historical origin of Chushu

Chishu is a solar term that reflects changes in temperature. The original meaning of "place" is "to stop" and "to stay". "Shuowen Jiezi" says: "Where it stops". "Department" means that the hot and unbearable weather has come to an end and the heat has begun to subside. "Three Heats" and "Three Volts" both represent high and extremely hot weather. When summer comes, dog days arrive; when dog days disappear, summer heat comes to an end.

The twenty-four solar terms include the "three summers", namely the minor summer solar term, the major summer solar term, and the final summer solar term. In order, they are the early summer heat, the heat stroke, and the late summer heat. There is also a solar term "Beginning of Autumn" sandwiched between the "Three Summer Heats". After the Beginning of Autumn, the end of summer heat comes, and the period of intense heat is relatively long. Longer summer heat is beneficial to crop growth and yield. The ancients called the period from the beginning of autumn to the autumnal equinox "long summer".

The "Dog Days" involves the four solar terms of Little Heat, Great Heat, Beginning of Autumn, and End of Summer. By the time of End of Summer, the Dog Days have passed or are coming to an end. The subsidence of summer heat is a slow process, and it does not mean that the weather will cool down immediately after the heat drops. Although it is still hot during the summer season, the temperature has begun to show an overall downward trend.

Reference for the above content: Baidu Encyclopedia - End of Heat