The solstice of summer means that summer is coming. On the summer solstice, the sun shines directly on the tropic of cancer, so the summer solstice is the longest day in the northern hemisphere. During the summer solstice, the rainstorm will continue and the temperature will continue to rise. Jianghuai area will enter the rainy season. In ancient China, the solstice of summer was still the day of ancestor worship, so it was necessary to worship the gods and ancestors and avoid summer.

Summer solstice is one of the 24 solar terms. Every year on June 2 1 or 22 of Gregorian calendar, the sun moves to 90 degrees of the yellow meridian, which is the summer solstice. At this time, the position of the sun directly on the ground reaches the northernmost point of the year, almost directly on the Tropic of Cancer, and the sunshine time in the northern hemisphere is the longest. After the summer solstice, Yin Qi began to grow and Yang Qi began to decline.

On the day of summer solstice, the sun directly reaches the northernmost part of the year, almost directly to the Tropic of Cancer (23 26' north latitude), and the daytime in the northern hemisphere reaches the longest, and the farther north it is, the longer it is. For example, the daily length of Haikou in Hainan is about 13 hours, while that of Mohe in Heilongjiang is about 17 hours, and that of Beijing is about 15 hours. Moreover, this day is the day when the sun reaches the largest range in a year in the northern hemisphere, and it is also the day when the sun is the highest from the earth. From summer to the future, the position of direct sunlight on the ground gradually moves southward, and the daytime in the northern hemisphere is shortened day by day. There is a folk saying that eating noodles on the solstice in summer will shorten the day. At this time, the southern hemisphere is in the middle of winter.