Kentucky Governor Andy Beshear said eight people had died in his state and suggested at a news conference on Sunday that the total could go up.
Hundreds of people stranded in flood waters, many stuck in their cars, had been rescued, and Beshear warned residents to "stay off the roads right now and stay alive".
In Georgia, the ninth death was recorded after a man lying in his bed was struck by an uprooted tree that crashed into his home.
Kentucky, Georgia, Alabama, Mississippi, Tennessee, Virginia, West Virginia and North Carolina were under some type of storm-related alert this weekend. Almost all of those states suffered catastrophic damage in September from Hurricane Helene.
Between the eight states, more than half a million households were without power on Sunday night, according to poweroutage.us.
A bulk of the death and destruction appears to have occurred in Kentucky, where a mother and her seven-year-old child and a 73-year-old man were among the dead.
Some parts of Kentucky received up to 6in (15cm) of rain, National Weather Service (NWS) figures show, resulting in widespread flooding issues.
The rapid influx of rain caused river levels to rise quickly and trapped vehicles in feet of water, images posted online show.
Governor Beshear wrote on X that there were over 300 road closures.
He also said that he had written to the White House requesting an emergency disaster declaration and federal funds for affected areas, according to the BBC's partner CBS News.
President Donald Trump approved the declaration on Sunday, authorising the Federal Emergency Management Agency (Fema), which he has suggested abolishing, to co-ordinate disaster relief efforts.
Officials have cautioned that the worst of the flooding is not over yet.
AzVision.az
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