The central region was hit with up to 50-60 mm of heavy rain per hour, with some areas in the northeastern province of Gangwon recording as much as 180 mm per hour from Friday to Saturday morning, according to the Korea Meteorological Administration (KMA).
The authorities issued heavy rain warnings for the Gangwon region and some areas in Gyeonggi Province as of 11:00 a.m. They also issued heavy rain advisories in parts of South Chungcheong Province, including Daejeon and the administrative city of Sejong, the KMA said.
Many roads were flooded by the downpour across the country, but no serious damage such as house flooding has been reported so far.
Some traffic accidents were reported, with a few people rescued from water in the central provinces, it added. No flights or shipping operations have been canceled.
The downpour is expected to help end the prolonged drought that had affected many paddy fields in provincial areas. A major dam in a western central province has recovered its water reserve rate to the first double-digit figure since May.
The weather authorities expected more rainfall over the weekend, with the forecast of some 30-80 mm of heavy rain in Seoul and the central provinces.
In contrast, the popular resort island of Jeju off the country's southern tip has experienced scorching heat this week, due largely to the oceanic climate, the authorities said.