JOIN USKorean Central Television and Korean Central Broadcasting Station said Chongdan County in South Hwanghae province had received 522 millimetres (more than 20 inches) of rain in 12 hours on Tuesday, South Korea's Yonhap news agency reported.
More than 14,200 hectares (35,000 acres) of farmland in the county were flooded along with a further 10,200 hectares in Yonan County, both in the west of the country, northwest of Seoul, it said.
It said that other counties were suffered heavy rain over the weekend, and that in Yonan alone, 13 bridges were destroyed, while roads and railways across the province were also damaged.
There was no word on casualties.
The floods will deepen concerns about North Korea's ability to feed its people, who already face severe food shortages.
North Korea has relied heavily on international aid to feed its 24 million people since natural disasters and mismanagement devastated its economy in the mid 1990s and Pyongyang has stepped up appeals for food aid this year.