June 21 is the summer solstice, when the sun shines directly on the Tropic of cancer, which is the longest day of the year in the northern hemisphere; December 22 is the winter solstice, when the direct point of the sun in the southern hemisphere is on the Tropic of cancer, which is the longest day of the year in the southern hemisphere.
Introduction to summer solstice
The summer solstice is not only one of the 24 solar terms, but also one of the four seasons and eight festivals in ancient times. It has been a custom to worship gods and ancestors at the summer solstice since ancient times. In addition, there are folk customs such as summer solstice, avoiding ambush in summer, clearing and tonifying.
After the summer solstice, although the direct point of the sun begins to move southward from the Tropic of cancer, the days in the northern hemisphere begin to shorten gradually, and the noon sun height also begins to decrease day by day for the Tropic of cancer and its areas to the north, because the heat radiated by the sun to the ground is still more than that radiated from the ground into the air, the temperature will continue to rise for a period of time in the future, Therefore, there is a saying that the summer solstice is not hot. （YiNianBaiZhouZuiChangShiNaYiTian）