Rain is the second solar term of the year. "Between two dimensions, ninety-one degrees and five sixteenths of a degree" is evenly divided into six solar terms, each solar term accounting for fifteen days. So fifteen days after the winter solstice is the minor cold, fifteen days after that is the severe cold, and fifteen days after that is the beginning of spring. Fifteen days after the beginning of spring, it rains. The date of the rain solar term is calculated in this way.

Wu Cheng, a Yuan Dynasty man, said in his work "The Collection of Seventy-Two Hours of the Moon Order": "In the first month of the first month, the sky generates water, and the beginning of spring belongs to wood. However, what generates wood must be water, so the beginning of spring will continue. "Rain. And when the east wind thaws, it disperses into rain." Rain means that the spring breeze gradually blows across the earth, the ice and snow melt, and even the air in the north begins to become moist, showing a prosperous scene everywhere.

Meteorological changes of rain

From a meteorological point of view, after the "rain", the maximum temperature in most areas of China can generally rise above 0℃. Although it has entered the rainy season in spring, But there is no breath of spring yet in most parts of northern China.

The average temperature in many areas in the south is above 10℃. At this time, rapeseed, winter wheat, etc. generally turn green and grow, and have higher requirements for moisture. As the saying goes, "Spring rain is as expensive as oil." Suitable precipitation is very important for the growth of crops. In North China, Northwest China and the Huanghuai region, precipitation is generally less at this time. If there is little rain in early spring, timely irrigation before and after the rain will be beneficial to the growth of crops.

Reference for the above content: Beijing Daily-How does the rain solar term come about

Reference for the above content: Baidu Encyclopedia-Rainwater