At least 30 people have now died in the Appalachia region of eastern Kentucky, as the region braces for more rainfall.
At least six children – including four siblings, aged one to eight, who were reportedly swept from their parents’ grip – are among the dead.
Kentucky Governor Andy Beshear said the death toll would continue to rise as “hundreds” remain unaccounted for.
More than 12,000 households remain without power, and hundreds of homes and businesses have been flooded.
The damage to roads, bridges and other infrastructure will take millions to repair, the governor said on Monday.
Mr Beshear, who toured some of the hardest-hit neighbourhoods over the weekend, said he had seen “houses swept away” and “schools ruined”.
This is the worst flash flooding the region has seen in decades.
Governor Beshear called the flood “the deadliest and the most devastating of my lifetime”.
Displaced locals have taken refuge in state parks, churches and mobile homes brought in by the state.
Many people “only have the clothes on their backs,” Mr Beshear said. “Everything is ruined.”
Scientists say climate change is triggering more extreme weather events like the Kentucky flooding.
President Joe Biden has declared the floods “a major disaster” and ordered federal aid to help local rescuers.
