The weather is erratic

The wind is rustling in the Five Dynasties and Three Dynasties, and the clouds are floating in 90 days, which means that the wind is blowing in three days and five days, and there are white clouds floating in the blue sky for nine days and ten days.

This sentence comes from Zhang Kan's Postscript of beginning of winter in the Song Dynasty. Although it is said that beginning of winter will come back in autumn and again in winter, Meng Dong is very cold. At this time, the weather is like the face of a little girl in spring. It has been windy for three days and five days, and it has been nine days and ten days. White clouds are floating in the blue sky. So this poem describes the beginning of winter in the south, which is slightly different from the phenology in the north.

Meteorological changes in early winter:

In early winter, the sun has reached the longitude of 225 degrees, and the northern hemisphere gets less and less solar radiation. However, there is still some energy in the heat stored on the surface in the second half of this year, so it is generally not too cold in early winter. In winter, the northeast wind and the north wind are the main winds.

In southern China, sunny, warm and comfortable "Xiaoyangchun" weather often appears from beginning of winter to Xiaoxue. There is a folk saying that "it's sunny in October". As the saying goes, "it's warm in August and warm in September, and it's sunny in October". Generally, it is not very cold in early winter in the south, but with the passage of time, cold air frequently goes south and the temperature gradually drops. ?

After winter, cold air frequently goes south, which may form cold wave weather accompanied by rain and snow. In the area north of Huaihe River in Qinling Mountains, cooling has become the norm at this time. In the northeast and northwest regions, it is already a scene of heavy snow, especially in the northeast Heilongjiang region, which is extremely cold and has entered the winter before the arrival of beginning of winter. The red and yellow scene in northwest autumn has not completely faded, but the snow has already fallen.

Refer to the above? Baidu Encyclopedia-beginning of winter