Autumn
Frost’s Descent
Oct 23–Nov 6
Frost's Descent (Shuangjiang) is the eighteenth solar term of the twenty‑four solar terms and the final solar term of autumn. The sun reaches the celestial longitude of 210°. It is the time of year when the diurnal temperature difference is greatest. This article explains in detail its climatic characteristics (a sudden drop in temperature, yin qi beginning to congeal), the phenological phenomena of its three pentads (jackals make offerings of the beasts, grasses and trees wither and shed their leaves, hibernating insects all bow down), the differences in farming activities between the north and the south, and folk customs such as appreciating chrysanthemums and ascending heights, eating ripe red persimmons, and stewing mutton. It also reminds people to guard against autumn dryness, autumn melancholy, and cold pathogens. It is a key transitional solar term from autumn into winter.
Frost's Descent (Shuangjiang), also known as Severe Frost, Frost Blade, and Frost Sword, is the eighteenth of the twenty-four solar terms and the final solar term of autumn. It occurs when the Big Dipper points to the terrestrial branch xu and the sun reaches the ecliptic longitude of 210°, typically falling on October 23 or 24 in the Gregorian calendar. Frost's Descent does not signify "frost descending," but rather indicates a sharp drop in temperature and a wide diurnal temperature range. On average across China, Frost's Descent is the period of the year with the greatest day-night temperature difference.
In high antiquity, solar terms were delineated by the "direction of the Dipper's handle." When the handle of the Big Dipper pointed toward the xu position (northwest), it marked the Frost's Descent solar term. From the Han dynasty to the end of the Ming dynasty, solar terms were determined using the "ping qi method" (equal-time method), employing the gnomon (guibiao) to measure the sun's shadow and determine the winter solstice. With the winter solstice as the starting point, each solar term was spaced approximately 15 days apart, placing Frost's Descent roughly 300 days after the winter solstice. During Frost's Descent, all things have reached completion and are gathered into xu; yang qi sinks into the earth, yin qi begins to condense, and the weather gradually turns cold, beginning with this solar term. The characteristic features of Frost's Descent are relatively cold mornings and evenings, comparatively warm midday, a wide diurnal temperature range, and pronounced autumn dryness. The ancients divided Frost's Descent into three pentads: in the first pentad, jackals begin to sacrifice their prey; in the second pentad, grasses and trees wither and their leaves fall; in the third pentad, all hibernating insects retreat into seclusion.
During Frost's Descent, most northern regions are already in the final stage of autumn harvest. In North China, Chinese cabbages are about to be harvested, and their late-stage management should be strengthened. In the south, however, it is the busy "Three Autumns" season: single-crop hybrid rice and late rice are still being harvested, early wheat is sown, early rapeseed is transplanted, and cotton is picked while cotton stalks are cleared away. People place great importance on Frost's Descent, and various customs are observed across regions, such as warding off misfortune, sweeping tombs, admiring chrysanthemums, and climbing high to gaze into the distance. Meanwhile, in some parts of China, dietary customs during Frost's Descent include eating red persimmons, "stewing lamb," "stewing sheep's head," and "welcoming frost rabbit meat." Furthermore, during Frost's Descent, attention should be paid to preventing autumn dryness, autumn melancholy, and cold.
