Memphis, Tennessee - Fierce storms stretching up and down the Midwest and South killed at least four people overnight, officials said, with tornadoes and violent thunderstorms expected to persist into Thursday.

The Tennessee Department of Health reported three fatalities, while one person died in Missouri.

The storm damaged buildings, toppled trees, downed power lines, overturned cars and lifted roofs off homes across a vast swath of the US, photos on social and local media revealed.

The system, which stretched from Arkansas northeastward into Ohio, produced heavy rains and flash flooding that forecasters say could last for days.

"A multi-day, potentially historic heavy rainfall event may produce catastrophic and life-threatening flooding through Saturday," the National Weather Service (NWS) said.

Before the storm's arrival in Kentucky, Governor Andy Beshear warned residents that the state was "facing one of the most serious weather events we've had forecast."

Damaging winds and isolated tornadoes were possible into Thursday night, the NWS in Louisville warned.

As of Thursday, electricity was out for nearly 400,000 customers across the central-eastern US, according to the PowerOutage.us website.

A variety of damaging weather is expected in the coming days.

"All modes of severe weather will be possible" the NWS office in Little Rock, Arkansas reported Thursday, including "very large hail, strong gusty winds and even a few tornadoes."

Warning of "unsettled weather" the NWS in Lincoln, Illinois, posted on X that severe storms, including hail and damaging wind gusts, were possible into Friday.