As the saying goes, "a slight cold is not as good as a severe cold." Why is it the coldest, but it is called slight cold?

The slight cold in winter corresponds to the slight heat in summer, so it is called "slight cold".

In the slight cold season, the direct point of the sun is still in the southern hemisphere, and the heat in the northern hemisphere is still in a state of loss. The heat absorbed during the day is still less than the heat released at night, so the temperature in the northern hemisphere continues to decrease. After the winter solstice, the cold air frequently goes south, and the temperature continues to drop, and the temperature drops to the lowest during the slight cold and severe cold in a year. There is a folk saying that "it's 239 when it's a slight cold, and it's almost freezing with cold", which shows that it's a slight cold.

According to China's long-term meteorological records, the slight cold solar terms are colder than the severe cold solar terms in the north, and there is a saying in the north that "slight cold is better than severe cold"; But for some parts of the south, the lowest temperature in the whole year will still appear in the cold solar terms. The slight cold in northern China is colder than the severe cold, because there is relatively little "residual heat" on the surface, which has been released to the minimum by the slight cold.

In the south, the surface is relatively hot, and its "residual heat" was not released until the slight cold. In severe cold, the surface "waste heat" is exhausted and the temperature is minimized.

rural activity

Due to the large geographical span between north and south in China, different regions will have different production and cultivation for the same slight cold solar terms. In the north, in most areas, there is not much farm work in the fields, and all of them have winter holidays. The main task is to do a good job of keeping warm in vegetable pits and sheds, and to make fertilizer and accumulate fertilizer at home.

Winter fertilizer should be applied to wheat, rape and other crops in southern China, while in Hainan and most parts of southern China, it is mainly to do a good job in cold and antifreeze, store fertilizer and build water conservancy projects. Slight cold and severe cold are the periods with the least rainfall in a year.

In ancient China, the "slight cold" was divided into three stages: "First-class Yanbei Township, second-class magpies started their nests, and third-class pheasants started their lives." The ancients believed that the geese among migratory birds migrated along the yin and yang, when the yang had moved, the geese began to migrate northward; At this time, magpies can be seen everywhere in the north, feeling the yang and starting to build nests; The word "pheasant" means singing. As April 9th approaches, pheasants can sing.