Grain Rain, known as Guyu in Chinese, means the growth of hundreds of grains. It falls on April 20th or 21st every year, when the sun reaches 30 longitude. According to Designate Collected Annotations on the 72, the earth begins to renew in the middle of March after the rain. When sowing the grain at this time, it is beneficial, therefore acquires the name. During this period, the poplar blossoms fall while the cuckoos chirp, willow catkins flying, peony sprouting, cherry ripening. All these scenes show that it is at the end of the spring. At this time, the temperature in the south rises. Generally speaking, the average temperature in the end of April has reached between 20 and 22 Celsius degrees, except the north part of South China and parts of west. The temperature increases by 2 Celsius degrees or above when compared with the middle of April. There will be one or two days when high temperatures appear in the southeast part of China. People begin to feel hot. River valley with low altitude enters summer.

In ancient China, Grain Rain was divided into three Hous (Hou, a unit for timing in ancient; five days make a Hou): in the first Hou, the duckweed begins to grow due to lots of rain; in the second Hou, cuckoos chirp to remind people of sowing seeds; in the third Hou, the Hoopoes appear on the mulberry.

During Grain Rain time, the westerly jet of East Asia once again weakens and moves northward. The warm air in the South China gets active; the waves of West belt from the west to east become frequent; low pressure and cyclone increase gradually. Because of all these factors, consecutive rain and storms occur.

Grain Rain is the last solar term in spring when the seedlings in the fields lack rain; hence, there is a saying which goes, “Rain in spring is as precious as oil”. In most parts of Southern China, rainfall is abundant. In the end of April, rainfall is around 30mm to 50mm. The first heavy rain each year falls on during this time, which is quite beneficial to the growth of rice, corn and cotton.