People holding umbrellas walk near the Gwanghwamun Square in Jongno-gu, central Seoul, Wednesday. (Yonhap)

South Korea remained on high alert for torrential downpours Wednesday as heavy rains hit the Seoul metropolitan area and parts of northern Gyeonggi Province, causing rush-hour traffic disruptions and home evacuations.

Heavy rains of 100.9 millimeters per hour had battered Munsan in Paju, Gyeonggi Province, for an hour until 7:03 a.m., while Singok-dong in Uijeongbu, just north of Seoul, received 103.5 mm of rain for an hour from 6:22 a.m.

Also, nearly 300 reports regarding heavy rains were reported to the Gyeonggi Bukbu Provincial Police's 112 situation room as of Wednesday at 9 a.m., of which 200 cases have been addressed, officials said.

Residents in Nowon-gu in northern Seoul, Jungnang-gu in eastern Seoul, and Guri in Gyeonggi Province were alerted at around 9:33 a.m. as more than 50 mm of rain was hitting the area.

Meanwhile, the weather agency predicted that heavy rains would continue to drench much of the nation until Thursday, with some regions forecast to receive up to 200 mm of rain.

The state weather agency issued its first emergency text message warning of torrential rains this year on Wednesday for the Seoul metropolitan area and parts of northern Gyeonggi Province. The Korean Meteorological Administration directly issues heavy rain alerts when rainfall exceeds 50 mm per hour, 90 mm in three hours or when the hourly precipitation rate surpasses 72 mm. The alerts inform people to stay alert during hazardous weather conditions and swiftly evacuate if necessary. Officials said six heavy rain alerts were sent last year to the greater Seoul area.

Flood advisories were also issued in Seoul's ten districts as of Wednesday noon: Gangdong, Gangseo, Eunpyeong, Mapo, Jongno, Seodaemun, Seongbuk, Gangbuk, Songpa and Nowon districts.

The entrances to 29 streams within the capital area were restricted, and the Dongbu Arterial Road and four parking stations along the river were closed at around 8:45 a.m. Restrictions for seven streams were lifted, and the Dongbu Arterial Road also reopened later in the day as the water levels of the nearby streams went down.

The weather agency forecast that 30 to 60 mm of heavy rains and up to 70 mm of rain per hour, accompanied by strong winds, thunder and lightning, will hit the metropolitan region, the northern part of Gangwon Province and northern parts of North Chungcheong Province from Wednesday afternoon until Thursday morning.

Hundreds of people evacuated their homes as massive monsoon rains hammered the country.

A total of 407 households and 560 residents nationwide relocated to nearby areas for safety reasons as of 11 a.m., according to the Central Disaster and Safety Countermeasure Headquarters. No casualties have been reported by the press time.

Torrential rains also led to disruptions in train operations.

Korea Railroad Corp. said Wednesday that it had suspended operations between Mangwolsa Station and Deokjeong Station on the Gyeongwon Line for 50 minutes due to the rain. Korail's operating guideline states that trains wait at the nearest stations when the rainfall exceeds 65 mm per hour. It resumed operations at around 8:50 a.m.

To prevent flooding in the area, the Korea Hydro & Nuclear Power Co. opened the two floodgates in Chuncheon at noon to discharge up to 250 metric tons of water per second so that the water could flow downstream and adjust the dam's water level. At the same time, the nearby Uiam Dam also opened its floodgates to release up to 500 tons of water per second.