Daeseo (Kor. 대서, Chin. 大暑, lit. Major Heat) is the twelfth of the twenty-four solar terms. It follows Soseo (Kor. 소서, Chin. 小暑, lit. Minor Heat) and precedes Ipchu (Kor. 입추, Chin. 立秋, lit. Beginning of Fall). Daeseo falls on the sixth lunar month and occurs around July twenty-third on the Gregorian calendar. On this day, the sun reaches the celestial longitude of 120°.
This solar term marks the hottest period of the year and follows the end of the rainy season, prompting an old saying: “even the goat’s horns melt on Daeseo.” The day often overlaps with Jungbok (Kor. 중복, Chin. 中伏, lit. Middle Dog Day, the second of the three hottest days of the year), during which people prepare special festive foods and drinks and escape from the heat to nearby valleys with streams. When the monsoon season continues late, Daeseo can also bring a heavy rainfall.
Daeseo is the time when farmers weed and prepare compost. Juicy summer fruits such as melon and watermelon and vegetables that ripen in this period are considered to taste better than at any other time of year. Wheat and barley are also ready to be harvested early around Daeseo.