An intersection in Siheung, Gyeonggi Province, is closed after flooding Thursday, when a heavy rain warning was in effect. [Yonhap]
An intersection in Siheung, Gyeonggi Province, is closed after flooding Thursday, when a heavy rain warning was in effect. [Yonhap]

Rain is expected to begin Friday, the Constitution Day holiday, and persist throughout the long weekend, with little chance of clear skies. Extreme rainfall has been forecast for some regions.

Rain will fall throughout the holiday period, according to Yonhap. Extreme rainfall is forecast particularly on Saturday, centered on the central regions and North Gyeongsang Province.

Through Friday, a stationary front will bring rain to areas south of the Chungcheong provinces. However, rain is also expected in southwestern Gyeonggi Province on Thursday night and in the Greater Seoul metropolitan area on Friday night.

Forecast rainfall through Friday is 30 to 80 millimeters for the Honam region, Busan, Ulsan and South Gyeongsang Province; 20 to 60 mm for the Chungcheong provinces, Daegu and North Gyeongsang Province; 5 to 10 mm for Jeju; and around 5 mm for southwestern Gyeonggi Province.

Over the weekend, a mesoscale low-pressure system is expected to develop along the stationary front, widening the rainfall area and intensifying precipitation compared to earlier in the week.

Extreme rainfall of 50 to 80 mm per hour is forecast in southern Gyeonggi Province in the early hours of Saturday (3 to 6 a.m.). Northern South Chungcheong Province can expect it from early Saturday morning through midmorning, and the central and southern inland areas and mountain zones of Gangwon Province and the central and northern parts of North Chungcheong Province from Saturday morning through late morning.

Forecast rainfall for Saturday is 50 to 150 mm for the Greater Seoul metropolitan area — with more than 200 mm possible in parts of southern Gyeonggi Province — and 30 to 80 mm for Gangwon Province, North Jeolla Province, central and northern North Gyeongsang Province, and Ulleungdo and Dokdo, with more than 150 mm possible in central and southern inland areas and mountain zones of Gangwon Province. The western five islands, Daegu and southern North Gyeongsang Province can expect 20 to 60 mm; North Chungcheong Province 50 to 100 mm, with more than 150 mm possible in central and northern parts; and Gwangju, South Jeolla Province, Busan, Ulsan, South Gyeongsang Province and Jeju 5 to 40 mm.

Rain is expected to continue through Monday morning in the central regions and through Monday evening in the southern regions, meaning total accumulated rainfall will be considerably higher.

Heavy rain has already fallen across the country this month, and with another round of intense precipitation on the way, authorities are urging thorough precautions to prevent damage.

Temperatures will not be especially high while it rains, but high humidity will keep conditions oppressively muggy. Nighttime temperatures are not expected to drop sufficiently, meaning tropical nights — when the overnight low stays at or above 25 degrees Celsius — will be widespread.

On Friday, morning lows are forecast at 21 to 25 degrees Celsius and daytime highs at 27 to 32 degrees Celsius.

Forecast lows and highs for major cities on Friday are: Seoul 23 and 32 degrees, Incheon 23 and 31, Daejeon 23 and 30, Gwangju 25 and 30, Daegu 24 and 32, Ulsan 24 and 30, and Busan 24 and 29.

On Saturday, morning lows are forecast at 20 to 25 degrees Celsius and daytime highs at 27 to 32 degrees Celsius. Strong gusts, thunder and lightning are expected over most coastal waters through the weekend.

Strong lunar gravitational pull will keep sea levels elevated through Friday. During high tide as Thursday night turns to Friday, atmospheric conditions could push sea levels even higher, raising the possibility of storm surge warnings for the Incheon and Gyeonggi western coasts, the Jeolla coast, the southern coast of South Gyeongsang Province and the Jeju coast.


woo@heraldcorp.com