On Saturday the 20th, heavy rain will fall over most areas nationwide through the morning.
Most of the rain will let up in the afternoon, but some areas will see rain continue through the afternoon in Yeongseo, Gangwon; northern North Chungcheong; and eastern South Gyeongsang; through the night in central and northern North Gyeongsang and along the southern East Sea coast of North Gyeongsang; and through the morning of the 21st in Yeongdong, Gangwon.
Expected rainfall is 10–40 mm in southern Gyeonggi, less than 5 mm in the five West Sea islands, and 5–20 mm in Seoul, Incheon, and northern Gyeonggi.
Yeongseo central and southern Gangwon, Yeongdong, Gangwon, Daejeon, Sejong, and South Chungcheong (excluding the northern West Sea coast), North Chungcheong, Busan, Ulsan, South Gyeongsang, Daegu, North Gyeongsang, and Ulleungdo and Dokdo will see 20–60 mm of rain (over 80 mm in places), and Jeju Island will see 10–60 mm (some areas 30–50 mm).
With heavy rain, water levels in valleys and streams can rise suddenly, so avoid camping and be prepared for possible backflow from sewers and the like.
Morning lows are forecast at 16–24 degrees, with afternoon highs at 21–29 degrees.
Morning lows in major areas are forecast at 18 degrees in Seoul, 18 in Incheon, 16 in Chuncheon, 17 in Gangneung, 19 in Daejeon, 20 in Jeonju, 21 in Gwangju Metropolitan City, 19 in Daegu, 24 in Busan, and 26 in Jeju.
Afternoon highs are 24 degrees in Seoul, 24 in Incheon, 23 in Chuncheon, 24 in Gangneung, 26 in Daejeon, 26 in Jeonju, 26 in Gwangju Metropolitan City, 27 in Daegu, 29 in Busan, and 28 in Jeju.
On Jeju Island, the maximum heat index will rise to around 31 degrees, making some areas sweltering. For the time being, some coastal areas of Jeju Island will see strong winds with instantaneous speeds around 15 meters per second.
Fine dust levels will be at a "good" level across all regions due to smooth atmospheric dispersion and the effects of rainfall.
Waves will run 0.5–3.5 meters in the East Sea nearshore and 0.5–2.0 meters in the West and South Sea nearshore. Thunder and lightning with gusts are expected in all seas, and strong winds with waves of 1.0–3.5 meters are expected in the far West Sea and the central and northern South sectors of the East Sea, raising the possibility of a high seas warning; caution is advised.
Wave heights in offshore waters within about 200 km of the coastline are expected to be 1.0–3.5 meters in the East Sea, 1.0–3.0 meters in the West Sea, and 0.5–2.0 meters in the South Sea.