What weather does March 9 refer to?

Three or nine days is the coldest time of the year.

The so-called "dog days are hot, March 9 is cold", and the coldest time of the year is from March 9 to April 9. Count nine cold days, that is, from the date of the winter solstice (the anniversary of the dry branch), count 19 every nine days until 9981, when the peach blossoms bloom, the weather will be warm. There is also a saying that "1999, 1999, there are cattle everywhere". After 1999, "the spring is deep and the sun is warm", and the spring ploughing season has arrived.

Extended data

Generation mechanism:

The coldest period in winter usually occurs after the winter solstice. During the winter solstice, the daytime is the shortest, the angle of direct sunlight on the ground is the smallest, and the sunshine intensity per unit area on the ground is also the smallest, so the ground gets the least solar heat every day, and the daily heat budget deficit on the ground has not reached the maximum. On the solstice after winter, although the day is growing day by day, the growth rate is very slow. From the winter solstice to the "March 9" period, the average daily growth is only about one minute. At the same time, the angle between the direct angle of the sun and the ground is slowly increasing. The daily heat budget of the ground is still in deficit, so it continues to lose heat and the ground temperature continues to drop.

The deficit of total heat balance on the ground only reached the maximum during "March 9 and April 9". Because the air temperature is mainly affected by the ground temperature, this leads to the lowest temperature during "March 9 and April 9". In addition, around March 9, the cold air mass in Siberia also developed to a very strong stage, and the frequent invasion of strong cold air is also one of the reasons for the low temperature. ?

Baidu Encyclopedia-Sanjiutian