In China, around November 22 of the Gregorian calendar every year, when the sun reaches 240 degrees of yellow longitude, the "light snow" solar term is delivered. Light snow is a solar term that reflects the change of precipitation, and the cloud of the "Seventy-two Candidate Explanations of the Lunar Order": "In October, the rain is thin by the cold, so it condenses into snow." The little ones are not prosperous".
This means that from the middle of the tenth month of the lunar calendar, the rain that falls in the sky solidifies into snow due to the cold, and the cold is not deep at this time, and the amount of snow is not large. After light snow, the temperature began to drop sharply, the average temperature was 3 4, down 3 5 from the previous solar term, the maximum temperature was 10 12, the lowest temperature was minus 4 5, and in very few years (such as 1993) it could reach about minus 20.
The depth of the permafrost can reach a maximum of 6 8 cm, which is still in the unstable freezing stage, and can still be cultivated in winter during this time of year in most years. Precipitation averages 6.8 mm, and there are many years when it falls less than 3 mm. According to meteorological records, in Beijing, Tianjin, Jinan, Zhengzhou, Xi'an and other places in China, the first snow period is in late November, that is, before and after light snow. However, in the northeast, Inner Mongolia, northern Xinjiang and other places, it had snowed a month before. In areas south of the Yangtze River, the first frost usually does not see until a month after a light snowfall.
The first time of light snow, "the rainbow is not seen", the second candidate of the beginning of spring, the "stinging insect is the beginning of the vibration", the third candidate of the beginning of spring, and the "fish is negative ice".