The Summer Solstice is the 10th of the 24 solar terms. It occurs when the sun's position in the zodiac points to the midsummer position; the sun's longitude is 90°; and it takes place on June 21st or 22nd of the Gregorian calendar. On this day, the sun's direct position on the ground reaches the northernmost point of the year, almost directly hitting the Tropic of Cancer. At this time, the daytime in all areas of the Northern Hemisphere reaches its longest of the year. For regions along and north of the Tropic of Cancer, the Summer Solstice is also the day with the highest solar altitude at noon in the year. 
The Summer Solstice marks the turning point of the sun's northward movement. After the Summer Solstice, the sun's direct point begins to move southward from the Tropic of Cancer. In the Northern Hemisphere, the days gradually become shorter. For regions in China located north of the Tropic of Cancer, after the Summer Solstice, the altitude of the noon sun starts to decrease day by day; for regions in China located south of the Tropic of Cancer, the altitude of the noon sun returns southward after the Summer Solstice, and then starts to decrease day by day after the sun returns to its direct position. 
High temperature, high humidity, and occasional thunderstorms are the weather characteristics after the Summer Solstice. The Summer Solstice is in the middle position of the summer season, namely the midday position. Midday belongs to the yang; although the yang energy is relatively abundant during the Summer Solstice and the daytime is the longest, it is not necessarily the hottest day of the year. At this time, the heat stored at the earth's surface is still accumulating and has not reached its peak. The Summer Solstice is one of the twenty-four solar terms and was also a festival in folk traditions during ancient times. Since ancient times, there has been a custom among the people to worship gods and ancestors on the Summer Solstice. Besides, after the Summer Solstice, people generally consume refreshing soups like clear nourishing soup, cool tea, and plumy tea to cool off.

Historical Origin 
The "Twenty-Four Solar Terms" are the product of ancient agricultural civilization. People discovered the seasonal changes in nature and gradually realized that the climate and phenological changes throughout the year also follow certain patterns. By observing the Big Dipper at dusk every day, people found that in different seasons, the orientation of the Big Dipper and the direction of the handle of the dipper were different. Therefore, the Big Dipper has long become a celestial symbol indicating the seasons. As written in "The Book of Rujing - Chapter of Circulation": "When the handle of the dipper points east, it is spring everywhere in the world; when it points south, it is summer everywhere in the world; when it points west, it is autumn everywhere in the world; when it points north, it is winter everywhere in the world." 
The Twenty-Four Solar Terms are specific festivals in the calendar that indicate the changes in natural rhythms and establish the "twelve months of the year". There are four seasons in a year, each lasting three months, with two festivals in each month. Each festival has its own unique meaning. According to Chen Xiling's "Adhering to the Regulations of the Calendar" [Summer Solstice]: "On the summer solstice, the sun reaches its northernmost point, the longest day, and the shortest shadow. Therefore, it is called the Summer Solstice. 'To' means 'extreme'." The name of the Summer Solstice comes from this explanation. At noon on the Summer Solstice, the sun is in an absolutely (almost) direct position of radiation, and a brief "no shadow when a pole is erected" phenomenon occurs in the regions along the Tropic of Cancer. This phenomenon only occurs in areas south of the Tropic of Cancer. 
Weather changes 
Temperature and precipitation: After the Summer Solstice, although the direct path of the sun begins to gradually move southward from the Tropic of Cancer, the days in the Northern Hemisphere start to gradually become shorter. However, since the heat radiated by the sun to the ground is still greater than the heat dissipated by the ground into the air, the temperature will continue to rise in the following period. Therefore, there is a saying that "it won't be hot without the Summer Solstice". As an old saying goes, "The hottest days are in the Summer Solstice period", and the true hot weather usually lasts from mid-July to mid-August in the Gregorian calendar. 
On the Summer Solstice, the position where the sun directly shines on the ground reaches the northernmost point of the year. In the Northern Hemisphere, the daytime duration reaches the longest of the entire year. During this period, most areas in China have relatively high temperatures, abundant sunlight, and crops grow rapidly. The physiological and ecological water requirements are also relatively high. After the Summer Solstice, the ground is strongly heated, and air convection is vigorous. Thunderstorms often form in the afternoon to evening. These heat thunderstorms come suddenly and go quickly, with a small rainfall area. People call this kind of thunderstorm "Summer Rain Crossing Fields and Holes". 
"Summer Solstice" marks the beginning of the hot summer. Although it is not yet the hottest time of the year, it is not far from the start of the "Summer Heat Period". From "Summer Solstice", after three "Ji Day" periods, the hottest period of the year, the Triennial Heat Period, begins. It is characterized by high temperatures, high humidity, and occasional thunderstorms. "Summer Solstice" marks the beginning of the "First Trimester of Heat". 
"Throne without shadow": On the summer solstice, the sun almost directly shines on the Tropic of Cancer, and at noon it appears to be in an absolutely (almost) direct position. In areas near the Tropic of Cancer, the phenomenon of "no shadow under the pillar" occurs. This phenomenon is only present in regions south of the Tropic of Cancer. There are two moments each year when the sun shines vertically onto the ground.