The summer solstice is the 10th solar term of the 24 solar terms. Douzhi Wu; The solar meridian is 90 °; The festival falls on June 21-22 of the Gregorian calendar. On the summer solstice, the position where the sun shines directly on the ground reaches the northernmost point of the year, almost directly on the Tropic of Cancer. At this time, the days in the Northern Hemisphere reach the longest time of the year. For the Tropic of Cancer and the regions to the north, the summer solstice is also the day with the highest sun height at noon.

The summer solstice is the turning point of the sun's northward movement. After the summer solstice, the direct sunlight point began to move southward from the Tropic of Cancer, and the days in the Northern Hemisphere began to get shorter. For China located in the north of the Tropic of Cancer, after the summer solstice, the noon sun height began to decrease day by day; For China, which is located in the south of the Tropic of Cancer, the noon sun height returns to the south after the summer solstice, and it starts to decrease day by day after the sun shines directly again. 

High temperature, high humidity, and occasional thunderstorms are the weather characteristics after the summer solstice. The summer solstice is in the position of mid summer, that is, the noon position, and the noon belongs to the yang; Although the summer solstice has a strong yang energy and the longest day, it may not necessarily be the hottest day of the year, so the heat near the surface is still accumulating and has not reached its maximum. The summer solstice is not only one of the 24 solar terms, but also a folk festival in ancient times known as the "Four Seasons and Eight Festivals". Since ancient times, there has been a custom of worshipping gods and ancestors during the summer solstice. In addition, after the summer solstice, people generally eat Ching bo leung soup, herbal tea, Suanmeitang, etc. to escape the summer heat.