A series of storms and tornadoes hit a number of small communities in Texas and Arkansas, killing at least five people.
At least three people were unaccounted and dozens were injured as the twisters damaged buildings and crippled life.
A couple in their late twenties died while trying to protect their 18-month-old girl from the storm in Nashville, Arkansas on late Sunday.
"It's a miracle that little girl survived," Howard County Coroner John Gray said.
In neighbouring Texas, a tornado pummeled the small town of Van and killed two people, damaging about 30 percent of the community, according to Chuck Allen, fire marshal and emergency management coordinator for Van Zandt County.
Three people were missing in the small town located some 112 kilometre southeast of Dallas.
Officials confirmed that the tornado was an EF3, with winds up to 140 mph (225 kmh), Allen said.
At least 42 people were injured, according to two East Texas hospitals. Four patients were in critical condition.
Fifty to 100 homes were either damaged or destroyed, Allen said.
The town's elementary and intermediate schools were also heavily damaged.
Preliminary reports indicate 20 to 25 tornadoes formed on Sunday in South Dakota, Iowa, Oklahoma and Texas, according to meteorologist Greg Carbin of the Storm Prediction Center in Norman, Oklahoma.
The storm system was expected to slowly move east, he said, with a low possibility of tornadoes in lower Michigan on Monday. Thunderstorms were forecast from Texas to the Great Lakes region.
The same storm system dumped 11 inches of rain in some places and caused widespread flooding.
Farther north, in Lake City, Iowa, a suspected tornado tore the roof from a high school as about 150 students, family and faculty attended an awards ceremony inside on Sunday night.
Earlier on Sunday, storms struck the small town of Delmont in South Dakota and hurt nine people.
Elsewhere, winter seemed to return briefly to parts of the Dakotas.
Winter weather advisories and warnings were posted for southeastern North Dakota and north-central South Dakota, with a couple of inches of snow and strong winds are expected. The same area experienced more than eight inches of snow over the weekend, breaking snowfall records for those dates in Rapid City.