Two children were injured and more than a dozen people were treated on the scene for minor injuries after the Franklin tornado.
The Angelina County Sheriff's Office said an eight-year-old and a three-year-old died when strong winds toppled a tree onto the back of their family's vehicle in Lufkin while it was in motion. The children were pronounced dead at the scene.
There were reports of multiple injuries in the Robertson County town of Franklin, the NWS said, and CNN affiliate KWTX reported widespread damage there.
The entire town of Franklin and neighboring Bremond lost electricity, with power expected to be restored Saturday night.
In Texas, baseball-sized hail fell north of San Antonio, with larger hail falling closer to the Dallas-Fort Worth region.
The weather service said preliminary information showed an EF-3 tornado touched down with winds of 140 miles per hour (225.3 kph). The High Resolution Rapid Refresh model is showing numerous discrete supercells developing during this time frame and the potential for strong tornadoes.
The storms ripping through the South in recent days have leveled trees and homes and caused power outages, according to reports.
There is an enhanced risk for severe weather on Sunday from Georgia to OH, including Atlanta; Charlotte; and Charleston, West Virginia.
CNN meteorologist Chad Myers said the warm air present during the afternoon enhanced the atmosphere's instability, creating more energy for storms to tap into and aiding in their development.
He said the threat for severe weather is greatest at such times.
Severe storms will develop later Saturday in eastern Texas, Louisiana and western MS that will likely tap into strong wind shear and develop unsafe supercells in the afternoon hours.
Heavy rains and storms raked MS into the night Saturday as the storms moved east.
The energy from warm afternoon temperatures will diminish, but the risk for tornadoes will not be over.
(ABC News) Violent tornadoes, destructive winds and large hail are all possible from eastern Texas through Louisiana and Mississippi.
Tornadoes at that time can be especially unsafe since they are hard to see and people are less likely to receive warnings while they're asleep.
The National Weather Service says thunderstorms are expected Saturday from Texas to Alabama.
On Sunday morning, storms will congeal into a line that will likely stretch from the Florida Panhandle to Ohio.
(ABC News) The threat for severe weather moves into the Appalachians on Sunday.
John Moore, a forecaster with the National Weather Service in Jackson, says a twister was reported Saturday in the Vicksburg area of MS and was indicated on radar.
The line of storms will impact the Appalachian Mountains on Sunday evening as they begin to lose their severe potential.
Georgia's Augusta National Golf Club is included in the slight risk area Sunday as the Masters concludes.