A major clean-up operation is under way in several states in America's south and mid-west after tornadoes and storms left at least 20 dead.
Hardest hit was Alabama, where at least eight people died when a tornado struck a high school building on Thursday. Nine more people died in Georgia.
US President George W Bush is due to visit some affected areas on Saturday.
The tornadoes were part of a major storm system that stretched across a swathe of the United States.
The US Storm Prediction Center (SPC) had earlier issued a rare "major severe weather outbreak" warning for the eastern third of the US.
Some of the worst of the destruction was reported in Enterprise, Alabama.
Eight teenagers who were inside the local high school died as winds blew out walls and collapsed part of the roof.
"They were in one particular wing which took a direct hit," Enterprise Mayor Kenneth Boswell said.
One other person in Enterprise died and at least 40 people were injured as the tornado, travelling at over 50mph (80km/h), swept through the town.
Alabama Governor Bob Riley, who visited the high school on Friday, said Enterprise had suffered "major and widespread damage".
"Everything I've seen today - the damage is truly remarkable," he told reporters. "To sum it up, it is horrific. I am truly amazed we didn't have more loss of life."
He said he would deploy 100 National Guard soldiers to help with recovery efforts.
A tenth person died in the town of Millers Ferry, in another part of the state, where high winds felled trees and flipped trailers.
Later in the day, at least nine people died in neighbouring Georgia.
Two people were killed and several more injured when a tornado struck near the Sumter regional hospital in Americus, Georgia, the state's emergency management agency said.
It was not clear whether the dead were patients. At the hospital, windows were shattered and cars had been thrown around. The ambulance fleet was reportedly destroyed.
A third person was reported killed in Taylor County, to the north, and six others in the southwest.
Georgia Governor Sonny Perdue was to fly to the affected areas to assess the damage, his spokesman said.
President Bush is expected to make stops in Georgia and Alabama on Saturday but White House officials have not yet confirmed where.
The tornadoes caused damage across several states
Mr Bush said: "Tomorrow I'm going down to Georgia and Alabama. I go down with a heavy heart.
"I go down knowing full well that I'll be seeing people whose lives were turned upside down by the tornadoes. I'll do my very best to comfort them."
In all, the US National Weather Service received 31 reports of tornadoes on Thursday from Missouri, Illinois, Alabama, Georgia and Florida.
A seven-year-old girl died as some of the first tornadoes touched down in Missouri around dawn.
The severe weather formed a band of storms stretching from Minnesota in the north to Louisiana on the Gulf Coast.
Further north, several mid-western states were hit by heavy snow and blizzards, which closed hundreds of miles of major roads.
Two people died when their car overturned on a slippery road in North Dakota, and another was killed while shovelling snow in Nebraska, the Associated Press reported.
Roads were also closed and flights cancelled in eastern Canada after heavy snow storms.
TORNADOES REPORTED IN THE US
People killed by tornadoes in southern US
Enterprise, Alabama: Eight dead at school, one elsewhere
Millers Ferry, Alabama: One dead
Americus, Georgia: Two killed when tornado struck hospital
Taylor County, Georgia: One dead
South-west Georgia: A further six people reported dead
Missouri: Seven-year-old girl killed