Guyu, Grain Rain, is the sixth and last solar term of spring, at the sun's longitude of 30 degrees, around the twentieth of April. It is a principal (zhongqi) term. Its name marks the season of steady, warm rains that swell the newly sown grain, the moisture on which the young crops depend. In the farming almanac it is the last call for late spring planting before summer, and it is closely tied in tradition to tea, the leaves picked around Guyu are especially prized, and to the sowing of cotton and rice seedlings. Being a solar marker, it falls near the same Gregorian date each year. These are the observances of the East Asian agricultural tradition, resting on the twenty-four-fold division of the tropical year into equal solar arcs.
Guyu, the Grain Rain term, falls at 30 degrees, around 20 April, and is a qi, or major, term, the last of the six solar terms assigned to spring before summer's terms begin with Lixia. Its name reflects the traditional expectation that rainfall at this point in the year is sufficient to nourish newly sown grain, and the term closes the spring sowing period in the traditional agricultural calendar of the North China Plain. In some regional folk traditions Guyu is associated with the god Cangjie, legendary inventor of Chinese writing, said in one account to have caused millet to rain from the sky in celebration when writing was created, a story linking the term's name to a mythic register distinct from its literal agricultural meaning.