In the dead of winter, it is usually not very cold before the so-called "Sanjiu Cold" and "Sanjiu Cold". Starting from the winter solstice, every "nine days" counts as a "nine", the first nine days are called "one nine" and the last nine days are called "two nine".
By analogy, the coldest period of the year is "three or nine days". From the beginning of the winter solstice solar term, it began to enter the "three or nine days." Strong cold air frequently goes south, the temperature drops suddenly and the weather is cold. Therefore, the solstice winter is really cold winter.
Extended data:
There are different versions of "99" in different places, but it is basically the coldest period between March 9 and April 9. For example, "Walking on the ice on March 9, April 9" is a widely circulated sentence in northern China. In Sichuan, there is a saying that "pigs and dogs froze to death in March 949".
The winter solstice solar term of 20 19 was on February 22nd, 65438, and it began to enter the cold stage of the year after the winter solstice solar term, while the coldest "Sanjiu" and "Jiu Si" were from June 9th to June 22nd, 2020 respectively. From this point of view, the coldest time is from 65438+1October 9 to 65438+1October 26 in 2020.
Baidu Encyclopedia-Winter