"There was a storm system that moved through the central US that brought everything from tornadoes to heavy snow to flooding in some areas," Pat Slattery, a spokesman for the National Weather Service.
"Missouri had more tornadoes in one day then they usually have in a season," he said.
The weather service had not yet confirmed reports that state was hit by at least 110 tornadoes.
Most of the dead were killed in mobile homes or in their cars as they tried to escape the tornadoes in Missouri.
The University of Kansas was closed after 60 percent of its buildings were damaged by a storm on Sunday that littered the campus with downed trees, broken glass and torn roofs.
In Illinois, public schools were closed and the governor orderednon-essential state employees to stay home Monday after tornadoes ripped through the capitol of Springfield.
In northern Texas, wildfires consumed more than 267,092 hectares with the largest of the fires stretching 72 kilometers long and 24 kilometers wide.
"This is probably one of the biggest fire days in Texas history," Warren Bielenberg, a spokesman for the Texas Forest Service.
Texas is in a severe drought and has been ravaged by more than 10,000 wildfires that have burned across at least 1.6 million hectares since late December.
Four people were killed Sunday in a chain-reaction accident caused by smoke obscuring the road while another three died in fires near Borger, Texas.