Why is the solstice in winter the coldest day?

Because the sun runs to 270 degrees of the Yellow Meridian from the winter solstice, the sun goes directly to the Tropic of Capricorn (also called the winter solstice daily line), and the sun is most biased towards the northern hemisphere. Therefore, the winter solstice is the most precious day and the longest night in the northern hemisphere. For all parts of the northern hemisphere, the winter solstice is also the day with the lowest sun height at noon all year round.

In winter solstice, although the sun is low and the days are short, the temperature in winter solstice is not the lowest in meteorology. In fact, because there is still "accumulated heat" on the surface, it is usually not very cold before the winter solstice, and the real cold is after the winter solstice. Because of the huge climate difference in China, this climatic winter is obviously late for most parts of China.

Extended data:

Winter solstice, also known as short day, short day, southern solstice and winter festival, winter solstice festival, Asian New Year, is both a solar term and a festival. The winter solstice is a solar term reflecting the direct sunlight movement. On the solstice of winter, the sun moves southward to the extreme, and the sun shines directly on the tropic of Capricorn, which is the place with the shortest day and the longest night in the northern hemisphere. From that day on, the direct sunlight point returned to the north, and the height of the sun in all parts of the northern hemisphere (China is located in the northern hemisphere) gradually increased, and the number of days also increased day by day.

The solstice in winter is the turning point of "South to North". For all parts of the northern hemisphere, the height of the sun rises and the sunshine gradually increases. According to the law of solar terms, beginning of spring is the starting point of the rising of "Yin and Yang" qi in Yang Qi. Since the beginning of spring, Yang Qi has changed and Yang Qi has risen. The beginning of spring marks the rebirth of everything and the beginning of a new cycle.

The solstice in winter is the starting point for the return of the sun. Since the winter solstice, the height of the sun has risen, and the day is getting longer and longer. The winter solstice marks the rebirth of the sun and the round-trip movement of the sun into a new cycle. Therefore, the ancients also regarded the winter solstice as a "good day". Among the eight festivals, the winter solstice is as important as New Year's Day in spring.