Heavy downpours on Monday night submerged roads, flooded metro stations and caused blackouts across the city and neighbouring provinces.
Some areas received the highest rate of rainfall in 80 years, Korea’s meteorological agency said.
Weather officials forecast the rain was likely to continue over several days.
Parts of Seoul, the western port city of Incheon and Gyeonggi province surrounding Seoul charted rainfall of over 10cm of rain per hour on Monday night, according to Yonhap news agency.
Meanwhile, Seoul’s Dongjak district recorded more than 141.5 mm of rain per hour – the highest rate since 1942, according to Korea’s Meteorological Agency (KMA).
Images published on Yonhap showed floodwater gushing down the steps of metro staircases, parked cars submerged up to their windows and people making their way across streets in knee-high water.
At least five people died in Seoul and two others in the neighbouring Gyeonggi province as of Tuesday morning, according to South Korea’s Central Disaster and Safety Countermeasures Headquarters.
The agency said four died after being trapped in flooded buildings, one was electrocuted, one person was found under the wreckage of a bus stop, and another died in a landslide. At least nine others were injured, and six others reported missing.
People struggle to hold onto their umbrellas in a crosswalk in the rain in Seoul, South Korea, 08 August 2022, as the rainy season revisits the country.
At least 163 people in Seoul have been made homeless and have taken shelter in schools and public facilities, according to Yonhap.
The downpour also affected public transportation, as flooded railroads forced suspension of railway services in Seoul and Incheon.
The KMA continued to issue heavy rain warnings across Seoul and surrounding metropolitan areas, and said it expected rainfall for the central part of the country to continue at least until Wednesday.