Cities across the South and Midwest braced for more destruction on Friday from a storm that has already leveled homes and businesses and killed at least seven people in three states this week.

From Arkansas to Michigan, communities were sifting through the debris left by heavy rainfall and high-speed winds that started Wednesday night. River towns and cities were eyeing rising waters and piling up sandbags ahead of more rain this weekend.

The National Weather Service on Friday morning warned of a “life-threatening, catastrophic and potential historic flash flood event” across the Lower Ohio Valley and the Mid-South to Lower Mississippi Valley. A flash flood warning was in effect for much of central and western Kentucky. Strong tornadoes and large hail storms were also possible in parts of Arkansas, Louisiana and Texas.

More than 30 tornadoes have already swept through Mississippi, Arkansas, Illinois, Kentucky, Missouri, Indiana and Tennessee, and millions are under flood warnings and watches.

Tornado damage in Selmer, Tenn., on Thursday.Credit…William DeShazer for The New York Times

In Tennessee, where at least five people were killed by the storms, including a teenage girl, several inches of rainfall throughout Thursday caused major floods and shut down roadways.

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