What is the coldest day of the year?

Not necessarily, it is impossible to get the exact date, because the temperature is related to many factors, but the coldest time in northern China usually occurs around the great cold solar terms.

It will be the coldest time of the year from the winter solstice solar terms to the "slight cold" and "great cold" solar terms. The day of "Winter Solstice" also marks the beginning of the countdown to nine. On this day, the ground gets the least solar heat in the shortest day, but at this time it can supplement the heat stored on the ground in summer and autumn, so the temperature is not necessarily very low. By March 9, the heat stored on the ground will be exhausted. As long as cold air comes, it will freeze, which is the coldest season.

Extended data:

Although the sunshine in the northern hemisphere is the least, it is not necessarily the coldest day on the winter solstice. The solstice in winter is the shortest day in a year. As the saying goes, "March and September are cold and mid-September is hot", which means March and September should be the coldest, but it is also related to the morning and evening in beginning of spring. This is a complicated question with no definite answer. When it is coldest is uncertain. But it must be in winter.

Climate is affected by many factors, besides latitude, there are topography, ocean currents, atmosphere (that is, the above-mentioned surface heating to atmospheric heating) and so on. Take the typical continental monsoon climate in China as an example. An important reason for the lowest temperature and coldest climate during the Great Cold to beginning of spring is the atmospheric movement. The westerly monsoon pushes to the distant ocean with overwhelming advantage, resulting in a continental climate with low temperature, drought and little rain.

Due to topographical factors, the southwest trade winds are blocked by the Himalayas and Hengduan Mountains, which cannot cover the hinterland of the mainland, thus forming a severe cold in the mainland. Even so, in Chinese mainland, which belongs to the north temperate zone, there is still an obvious phenomenon of north-south water division in winter, that is, the subtropical zone and the cold temperate zone are divided by the Qinling-Huaihe line, which is caused by topographic factors. The southeast coastal areas are greatly influenced by the ocean, and there will also be local weather different from the inland areas, which is also an atmospheric factor. In a word, latitude determines the difference between winter and summer on the general plane, and the specific climate difference is mainly in topography, atmosphere and other factors.