In Gunsan, 131.7mm of rain fell within one hour early Wednesday – more than 10 per cent of the area’s average annual precipitation.
Some rivers overflowed and roads were flooded by heavy rain, images on South Korean broadcasters showed, with people seen wading through waist-deep water in some areas.
The rainfall led to four deaths, the interior ministry said.
Rescuers found a body trapped inside an elevator after a studio apartment was flooded in Nonsan, South Chungcheong, early Wednesday, Yonhap news agency reported.
Another victim was found dead after being sucked into a drainage system while checking his crops in the city of Daegu, it said.
One man in a car, returning home from tending to his cattle, was swept into a stream – still inside his vehicle – in North Chungcheong. His body was retrieved nearly three hours later. A man in his 70s died after a house collapsed in a landslide in Seocheon, the news agency reported.
Train operators have suspended some services covering the southern region affected by the downpours.
“I ask that people refrain from going to underground parking spaces, underpasses and streams during heavy rainfall,” Interior Minister Lee Sang-min said in a statement.