On the day of the summer solstice, the position where the sun shines directly on the ground reaches the northernmost point of the year, that is, it basically shines directly on the Tropic of Cancer. On this day, the daytime in the northern hemisphere is the longest, and the farther north it is, the longer it is. There will be extreme daylight in the Arctic. The heat close to the surface continues to accumulate, and the temperature continues to rise. China has a continental climate, and the temperature will reach the highest in all parts of China from mid-July to mid-August.
Summer solstice, also known as "Summer Festival" and "Summer Solstice Festival" in ancient times. "Zhi" means extreme in the old saying. In China's traditional theory of Tai Chi Yin and Yang, the summer solstice is a solar term in which the sun's spirit rises to the extreme and frugality begins. In fact, although the yang is flourishing, it has lost its power, and the yin grows and the yang disappears.
At this time, the weather was hot, people lost their appetite, and began to lose weight. In addition, people generally thought that "Yin grows while Yang disappears", and people began to relax in summer, pay attention to diet and make preparations for the intense autumn agricultural labor. For example, Zhejiang likes to eat boiled eggs with red dates and stewed chicken with astragalus to nourish the body; In Guangdong province, there is a habit of eating dog meat. As the saying goes, "dogs on the summer solstice, let them go." That is to say, on the fourth day of the summer solstice, everyone kills dogs and eats meat to make up for themselves, so there is nowhere for dogs to hide. According to legend, killing dogs in the summer solstice originated from the year after Qin Degong ascended the throne in the Warring States period, and it was very hot in June, and epidemics prevailed. Qin Degong ordered his subjects to kill dogs to ward off evil spirits according to the saying that "dogs are yang animals, which can bring misfortune", and later formed the custom of killing dogs in the summer solstice. The folk song "Make summer, eat tonic food" also shows that tonic food began in long summer.