Swords, storms and possible twisters are expected to hit the southern plains and southeastern states on Memorial Day, on the heels of deadly tornadoes and floods.
Temperatures around 100F (38C) were forecasts from Jacksonville, Florida, south-east of Macon and Savannah in Georgia and on to Charleston, South Carolina, said National Weather Service (NWS).
"This is super hot for this time of year," said John Deese, a NWS forecaster in Peachtree, Georgia, near Atlanta. "This is a heat wave in the south and it's going to be here for a while."
Deese predicted high temperatures throughout the week, staying in the mid to high 90's.
The risk of strong tornadoes is moderate but they remain possible throughout the week for southeastern plain states hit by mortal twisters last week, the forecasts said.
A serious tornado killed two people in El Reno, Oklahoma late Saturday, injured at least 29 people and left hundreds homeless, officials said. Rescue workers searched for survivors in the small community ruins near Oklahoma City.
NWS said another tornado touched down the Tulsa area early Sunday, damaging structures, tree steering, and power line redirection.
Pete Snyder with NWS said officials had confirmed that a tornado caused damage in Tulsa suburb of Sapulpa and surrounding areas. Snyder said the area also suffered injuries from innings, which officials say exceeded 80mph.
The tornado was formed by a powerful storm system that rolled through the state. Four others were killed in the storm in Oklahoma, CNN reported.
At least seven people were killed by storms last week.
States including Nebraska, Oklahoma and Kansas as well as parts of Ohio will remain under flood watches and warnings throughout the week that rain, wind, hail and possible twisters are in the forecast, said David Roth of the NWS Weather Prediction Center in College Park, Maryland.
Parts of Arkansas meanwhile are preparing which meteorologists predicted will be the worst flood in recorded history along parts of the Arkansas River during the coming week.
NWS said in the statement that levee "over topping" is likely to have "significant effects on life and property across a very large area."
The Arkansas River reached 38.2 ft Sunday near Fort Smith, which surpassed the historic crest of 38.1
Spokeswoman Karen Santos said the town 80,000 residents on the border with Oklahoma were in "readiness and warning state ". She said a home was completely submerged and about 500 homes had either water very close or in them. The authorities predicted several hundred homes and businesses would flood by the time the river crests on Tuesday at 42.5ft.
Over the river, the small town of Moffett, Oklahoma, was populated around 120, immersed in Saturday afternoon, said Sequoyah County Emergency Management Director Steve Rutherford to Times Record in Fort Smith.
On Sunday afternoon, a National Guard helicopter was sent to rescue two military corps of engineers who had been caught in a building when the Arkansas River rose, said Melody Daniel, Emergency Management of Arkansas.
"The river had risen and spread to a point where the lock and dam building were no longer accessible by boat or road," said Daniel, who took video of the rescue at Trimble Lock and Dam. She said there were also several road closures.
The water flowing into the Arkansas River has come from rains in southeast Kansas and northeastern Oklahoma, said NWS meteorologist Willie Gilmore.
"All this water pulled into the tributaries that go into the Arkansas River," Gilmore said.
In Tulsa, the authorities advised residents of some neighborhoods to consider traveling to a higher ground because the river emphasizes the city's ancient living system.