The state weather agency forecast Thursday the torrential rain that swept across the upper part of the Korean Peninsula would move down to the Chungcheong and Jeolla regions.

According to the Korea Meteorological Administration, up to 150 millimeters of rain is expected in the Chungcheong and Jeolla Provinces from Thursday to Friday. The weather agency issued an alert warning of heavy rain in the regions. 

For Seoul and the metropolitan areas, up to 50 mm of rain is expected through the early hours of Friday.

The two days of downpours starting Tuesday pounded Seoul and parts of Gyeonggi and Gangwon provinces, leaving two dead and three injured. The heavy rain warnings issued for Gangwon and Gyeonggi provinces were withdrawn in the early hours of Thursday.

A 57-year-old man surnamed Jang was found dead in his home in Yangju, Gyeonggi Province, around midnight Wednesday. He is believed to have slipped and fallen on a marble staircase while draining water from his house in the heavy rain, according to police.

Police were also searching for people reported missing. Multiple witnesses reported that a man thought to be in his 30s was swept down along a strong current in Gongneungcheon, a stream in Yangju, around midnight.

A 68-year-old woman surnamed Choi was also reported missing in Cheorwon on Thursday morning. Her family has not been able to reach her since Wednesday. Choi is believed to have gone missing as she was moving to farmland, according to police.

On Wednesday, a 49-year-old man drowned after he was trapped in his car on a submerged expressway in Nowon, northern Seoul.

As of 7 a.m. on Thursday, the accumulated rainfall from Tuesday amounted to 524 mm in Goyang, 406.5 mm in Yangju, 449 mm in Uijeongbu, 365.5 mm in Dongducheon, 448.5 mm in Yeoncheon and 330 mm in Namyangju, Gyeonggi Province, the state weather agency said.

The recent sudden downpours are a rare event, with heavy rainfall defined as 20 mm to 30 mm of rain in two to three hours. In Cheorwon, Gangwon Province, the rain pounded to the tune of 108.5 mm in an hour, while areas such as Pocheon and Uijeongbu in Gyeonggi Province and Dobong-gu in Seoul saw around 80 mm of rain in an hour.

The seasonal change is one of the reasons behind the unexpected rainfall. As the warm high atmospheric pressure in the lower part of the Korean Peninsula meets the colder air coming from the upper regions, it creates strong rain clouds, according to the weather agency.

By Jo He-rim (herim@heraldcorp.com)