The 21st, which is the minor fullness (소만) indicating the start of summer energy, showed hot weather from the morning. In Seoul and some areas of Gyeongbuk, Gangwon, and Gyeonggi, the highest low temperature recorded on a May day.
According to the Korea Meteorological Administration, the low temperature in Seoul reached 23.0 degrees at 5:53 a.m. This was 8.9 degrees higher than the average. This also marks the highest low temperature on a May day since modern weather observations began in Seoul in October 1907. The previous record was 21.8 degrees on May 16, 2018.
Incheon also recorded the highest low temperature on a May day in history at 20.7 degrees, recorded at 5:50 a.m. Incheon is where modern weather observations began in Korea in August 1904, the earliest recorded in the country. This indicates the hottest May low temperature in about 120 years.
Additionally, Uljin (low temperature 23.4 degrees), Ulleungdo (23.3 degrees), Yeongdeok (22.0 degrees), Wonju (21.8 degrees), Gyeongju (21.8 degrees), Dongducheon (21.1 degrees), Icheon (20.8 degrees), Ganghwa (20.2 degrees), Paju (20.1 degrees), Taebaek (19.9 degrees), Hongcheon (19.5 degrees), Cheorwon (19.3 degrees), Inje (18.9 degrees), and Daegwallyeong (18.1 degrees) also set new records for the highest low temperature on a May day. However, these low temperature records could change as the temperature drops after sunset.
Pohang nearly set a record for a 'May tropical night.' The temperature in Pohang remained above 25 degrees until 11:30 p.m. the previous night, then barely dropped below 25 degrees. A tropical night is a phenomenon where the temperature does not drop below 25 degrees from 6:01 p.m. to 9 a.m. the following day. Pohang's overnight low temperature was recorded at 23.8 degrees at 5:19 a.m.
The Korea Meteorological Administration noted, 'Due to a high-pressure system located east of Japan, hot and humid southern winds will continue to result in unusually hot days for May.'
The expected high temperature for the day is between 19 and 31 degrees. In most areas, daytime temperatures will exceed 25 degrees, while southern Gyeonggi, inland Gangwon, inland Chungcheong, and southern inland areas will rise around 30 degrees. It will remain muggy until Thursday morning, the 22nd, when cool air from the northwest is expected to bring temperatures back to average levels.
There is also a forecast for rain that day. Rain is expected in the metropolitan area, inland Gangwon, mountainous Gangwon, northern Chungnam, southern Jeonnam, and western southern Gyeongnam until the morning, and in Jeju until late afternoon. In most areas, the rainfall will be less than 5 mm, but in northern Jeju, it is expected to be 5 to 20 mm, while other areas will receive 10 to 40 mm (up to 60 mm in the mountains). In the afternoon, scattered showers of 5 to 40 mm (5 to 30 mm in eastern Gyeonggi) may occur in eastern Gyeonggi, Gangwon, inland Chungcheong, inland Jeonbuk, Gyeongbuk, and northwestern inland Gyeongnam.