North Korean officials told the International Federation of Red Cross and Red Crescent Societies that 200 people were dead or missing across the country.
North Korean state media reported earlier Tuesday that "hundreds" were dead or missing since the rains began last week.
"The material damage so far is estimated to be very big," the official Korean Central News Agency said. "This unceasing heavy rain destroyed the nation's major railways, roads and bridges, suspended power supply and cut off the communications network."
Lysholm said a total of 63,300 families had been affected by the weather, which completely destroyed 30,000 homes.
Of those, 20,000 houses were in worst-hit Kangwon province, where blocked roads were preventing aid workers from assessing the damage, he said.
Some 100,000 hectares (247,100 acres) of land have also been washed away, Lysholm said, affecting the impoverished nation's already limited ability to feed its people.
"That really definitely has an impact on the food situation for this year and at least one or two years," he said.
Lysholm said the floods were the worst in a decade in North Korea. In the mid-1990s, natural disasters coupled with outdated farming methods and the loss of the country's Soviet benefactor sparked a famine that is estimated to have killed as many as 2 million people.
North Korea's official media also painted a dire picture of the damage caused by the storms, which continue to soak the peninsula.
"The heavy rain destroyed at least 800 public buildings, over 540 bridges, 70 sections of railroads and at least 1,100 vehicles, pumps and electric motors," KCNA said