Nine of the nine solar terms are coldest.

March 9 and April 9 are the coldest seasons of the year.

There is a folk saying that "it's cold in nine days, and it's cold in dog days", and "dog days" refers to the third "nine days" after the winter solstice, that is, the 19th to 27th days after the winter solstice. "Yanjing Age" said: "The winter solstice on March 9 is difficult." It means that it has entered the coldest stage in cold weather since March 9. So in winter, 3949 is the coldest stage, just close to the great cold in the twenty-four solar terms. Every year around 65438+1October 20th, there is a severe cold, which means the weather is extremely cold.