The number of tornadoes were spotted across the parts of Oklahoma,kansas,Iowa and Nabraska on saturday.
Five people have been confirmed dead after a tornado hit the north-west Oklahoma town of Woodward.Woodward News reported that two of those killed were children.
Tornado sirens sounded across Oklahoma City before dawn, and at least three possible tornadoes were reported west and north of the city, said Oklahoma Department of Emergency Management official Michelann Ooten.
More than 5,000 people who had gathered in Woods County, Okla., for a rattlesnake hunt scattered when a tornado touched down, said county emergency management director, Steve Foster.
In a video from The Woodward News that was posted on the Web site of The Oklahoman newspaper, a massive tornado can be seen whipping up debris in the brief moments when flashes of lightning brighten the dark sky.
"The threat isn't over with tonight, unfortunately. Severe weather is possible again tomorrow from east Texas and Arkansas and up into the Great Lakes," said Bill Bunting, chief of operations at the Storm Prediction Center, which is part of the National Weather Service.
It was just the second time in U.S. history that the center issued a high-risk warning more than 24 hours in advance. The first was in April 2006, when nearly 100 tornadoes tore across the southeastern U.S., killing a dozen people and damaging more than 1,000 homes in Tennessee.