At least seven people were killed Wednesday and several others were reported missing as a storm system forecasters called "particularly dangerous" swept across the heartland.
Officials said four people, including a 7-year-old boy, were killed in Mississippi, where multiple tornadoes were reported. An 18-year-old Arkansas woman was also killed when a tree blew over onto a house and crashed into her bedroom.
In Tennessee, the state's Department of Health confirmed that a man and a woman were killed in severe storms in Perry County, southwest of Nashville, but had no further details. The Tennessee Emergency Management Agency says the county has reported debris across roads and some communications issues.
MSNewsNow.com reported that three people were killed in Benton County, Miss. and two others were missing. Crews were searching house-to-house and in wooded areas to make sure residents were accounted for. Police there said several homes were blown off their foundations.
A 7-year-old boy died in Holly Springs, Miss., when the storm picked up and tossed the car he was riding in, officials said. Marshall County Coroner James Anderson says the boy's relatives in the car with him were taken to a nearby hospital for treatment.
Greg Flynn, a spokesman for the Mississippi Emergency management Agency, reported more than 40 injuries in six counties but said that number could rise as the night goes on.
A tornado also damaged or destroyed at least 20 homes in the northwest part of the state. Clarksdale Mayor Bill Luckett said the only confirmed casualty was a dog killed by storm debris. Planes at a small airport overturned and an unknown number of people were injured.
"I'm looking at some horrific damage right now," the mayor told the Associated Press. "Sheet metal is wrapped around trees; there are overturned airplanes; a building is just destroyed."
Television images showed the tornado appeared to be on the ground for more than 10 minutes. Interstate 55 was closed in both directions as the tornado approached, the Mississippi Highway Patrol said.
About 120 miles east of the tornado, Brandi Holland, a convenience store clerk in Tupelo, Mississippi, said people were reminded of a tornado that damaged or destroyed more than 2,000 homes and businesses in April 2014.
"They're opening all our tornado shelters because they say there's an 80 percent chance of a tornado today," Holland said.
In Arkansas, Pope County Sheriff Shane Jones said 18-year-old Michaela Remus was sleeping in a bedroom with her 1 1/2-year-old sister in the house near Atkins, about 65 miles northwest of Little Rock, when winds uprooted the tree that crashed through the roof, killing the teen. Rescuers pulled the toddler safely from the home.
"It's terrible that this happened, especially at Christmas," Jones said.
In Indiana, an an EF-1 tornado struck the south Indianapolis suburb of Greenwood, television stations showed pictures of damage, including a portion of a roof blown off a veterinary office.
In the small coastal town of Loxley, Alabama, Mandy Wilson watched the angry gray sky and told drivers to be careful as she worked a cash register at Love's Travel Stop.
"It's very ugly; it's very scary," Wilson said. "There's an 18-wheeler turned over on I-10. There's water standing really bad. It's a really interesting way to spend Christmas Eve eve."
In parts of Georgia, including Atlanta, a flood watch was posted through Friday evening as more than 4 inches was expected, the National Weather Service said.
The threat of severe weather just before Christmas is unusual, but not unprecedented, Storm Prediction Center meteorologist Greg Carbin told the Associated Press.
Twisters hit southeast Mississippi exactly a year ago, killing five people and injuring dozens of others. On Christmas Day in 2012, a storm system spawned several tornadoes, damaging homes from Texas to Alabama.
Emergency officials in Tennessee worried that powerful winds could turn holiday yard decorations into projectiles, the same way gusts can fling patio furniture in springtime storms, said Marty Clements, director of the Madison County Emergency Management Agency in Jackson, the state's largest city between Memphis and Nashville.
"If you go through these neighborhoods, there are a lot of people very proud of what they've put out and they've got stuff everywhere -- all these ornaments and deer and everything else," Clements said. "They're not manufactured to withstand that kind of wind speed, so they become almost like little missiles."
The national Storm Prediction Center in Oklahoma issued a "particularly dangerous situation" alert for the first time since June 2014, when two massive EF-4 twisters devastated a rural Nebraska town, killing two people. Center meteorologist Matt Mosier says a preliminary report showed that at least 14 tornadoes touched down in Mississippi.
The biggest threat for tornadoes was in a region of 3.7 million people in Mississippi, Tennessee and Arkansas and parts of Missouri, Illinois and Kentucky, according to the center.
Twisters were possible from midday Wednesday through the evening. and forecasters said that by Wednesday night, the severe weather threat could shift east into the southern Appalachian Mountain region.
Once the strong storms cleared out, warm temperatures were expected. Highs in Atlanta and Charlotte, North Carolina, on Christmas Eve were forecast to be in the mid-70s.