Soseo (Kor. 소서, Chin. 小暑, lit. Minor Heat) is the eleventh of the twenty-four solar terms. It comes between Haji (Kor. 하지, Chin. 夏至, Summer Solstice) and Daeseo (Kor. 대서, Chin. 大暑, lit. Major Heat). On the Gregorian calendar, Soseo falls around July fifth when the sun reaches the celestial longitude of 105°. As its name suggests, Soseo signals the beginning of the scorching summer heat.
This period is marked by a high degree of humidity and a great deal of rain due to the seasonal rain front that crosses the middle of the Korean Peninsula. Rice plants that have been transplanted from seedbeds twenty or so days earlier (around the Summer Solstice) usually start to grow roots around Soseo. The first weeding takes place on this day and the weeded grass is used for compost afterwards. At the same time, farmers who harvest two crops in a year sow soybeans, millet, or red beans in the fields where the winter barley had grown. Many fruits and vegetables appear at this time, and the first harvests of barley and wheat can be collected and used to produce food.