Some 70 mm of rain per hour pounded the Seoul metropolitan area on Tuesday afternoon, leaving four missing and traffic severely congested. Lightning caused an explosion that led to one death. Over 400 cases of flooding were reported in Seoul alone.

Pocheon in Gyeonggi Province had the heaviest precipitation of 198.5 mm, followed by Namyangju and Uijeongbu in the province with 191 mm and 190.5 mm. Next were Dongdaemun district with 180 mm and Nowon district with 173.5 mm, both in Seoul.

Pedestrians walk through heavy rain in downtown Seoul on Tuesday. /Yonhap

Thunderstorms lashed Seoul and Gyeonggi Province through the night and rain kept pouring until early Wednesday morning, affecting traffic in the morning rush hour.

A mass of hot and humid air from the south collided with a cold and dry air mass over the Korean Peninsula, forming strong precipitation clouds, the Korea Meteorological Administration said. The rain will continue until Thursday and the central regions will likely see up to 300 mm of rain, it added.