One person was reported killed in a suspected tornado strike on a Louisiana home, and two others were reported dead after another storm hit around a community about 55 miles (90 kilometers) west of the north Alabama city of Huntsville.
Lawrence County Coroner Scott Norwood in Alabama said the two people killed were husband and wife. Authorities said the injured people included a 7-year-old-child who was taken to a hospital in Birmingham. Authorities did not release names of the victims.
The area was filled with debris and downed trees when first responders arrived.
"It was total chaos," Norwood told reporters. "We had to make due the best we could."
The storms prompted numerous tornado watches and warnings Monday.Some cities opened shelters as a cold front collided with warmer air over northern Gulf Coast states and temperatures were expected to plunge. The National Weather Service said the severe weather threat could last into Tuesday.
The Louisiana death was attributed to an apparent tornado that struck a residential area in Vernon Parish. Details were not immediately available, said Chief Deputy Calvin Turner. He said authorities feared others could be hurt, since crews were still trying to reach hard-hit areas.
In nearby Alexandria, Louisiana, about 200 miles (320 kilometers) northwest of New Orleans, crews cleared roads and restored power late into the night, working in a chilly mist.
Children in a church school were moved to the church before the tornado ripped off the school's roof, said Cpl. Wade Bourgeois, spokesman for the Alexandria Police Department. Among the hardest-hit spots was the Johnny Downs Sports Complex, which he said may have suffered "total damage." The complex includes five full-sized soccer fields, more than 10 smaller ones, and eight baseball diamonds.
"Fortunately we have no reports of any deaths or serious injuries," he said of the Alexandria area.
Meteorologist Donald Jones of the National Weather Service office in Lake Charles said it appeared the twister that hit part of Alexandria also struck near the town of DeRidder on an "absolutely ridiculous" path estimated at 63 miles (101 kilometers) long.
"I don't know what our records for the longest total in this area is, but that's got to be pretty damn close to it," he said.
Jones said storm surveyors will find out whether the tornado went the entire distance along the ground or touched down in spots along the way.
Three people were injured, at least one of them very seriously, by an apparent tornado that hit Amite County, Mississippi, Monday afternoon, county emergency director Grant McCurley said.
Some houses were destroyed and others severely damaged, he said. The number wasn't known Monday night because crews couldn't get to them all — downed trees tangled with power lines blocked county roads and state highways.
McCurley said damage was spread across the county, which adjoins the southeast Louisiana state line.
Four counties eastward, seven women were taken to a hospital from a heavily damaged group home in Sumrall, Mississippi. Injuries were minor, Sheriff Danny Rigel told WJTV. Damage on the men's side of the Douglas Graham Group Home was less severe than on the women's side, Lamar County emergency management director James Smith toldWDAM-TV.
That tornado cell sprang up in Tangipahoa Parish, Louisiana and went through Washington Parish on its way into Mississippi, said meteorologist Phil Grigsby of the National Weather Service office in Slidell.
The Storm Prediction Center reported two other people suffered minor injuries from flying debris after storms moved into Mississippi, and multiple trees fell atop homes and vehicles in Edwards, east of Vicksburg.
In Guntown, Mississippi, near Tupelo and about 260 miles (420 kilometers) north-northeast of Amite County, an apparent tornado destroyed a church and damaged dozens of homes.
Pastor Carl Estes searched through the debris of Lighthouse Baptist Church for books, photos or any other salvageable items, the Northeast Mississippi Daily Journal reported. The storm flattened the building, which Estes said was emtpy at the time.
Church member Shane Keith told the newspaper he rushed here after the storm and found pews tossed around the hillside.
"I wanted to cry, I really did" Keith said. "I mean, I just got baptized last year and this means a lot to me, this place right here."
Mississippi State Sen. Chad McMahn of Guntown said he toured a subdivision where an estimated 35 homes had been damaged.
As the storm system pushed into Alabama on Monday evening it toppled trees and power lines and kicked up more suspected tornadoes. The Colbert County Emergency Management Agency said buildings were damaged in the Colbert Heights area and that multiple roads were blocked.
School systems in Alabama, Louisiana and Mississippi dismissed students early and canceled afternoon events and activities.
Forecasters said tornadoes, hail and winds blowing at 70 mph (115 kph) posed the greatest threat as a cold front moved across the region in an easterly direction.
Tornadoes in December aren't unusual.
Monday was the 19th anniversary of a Southeastern tornado outbreak that produced a twister that killed 11 people in Tuscaloosa, Alabama. Storms on Dec. 1, 2018, spawned more than two dozen tornadoes in the Midwest.