Oklahoma Gov. Mary Fallin declared a state of emergency in a dozen counties Thursday, after multiple tornadoes and severe flash flooding left one person dead and at least 20 others injured.
One woman died after she was trapped in an underground shelter, Oklahoma City police said.
"She was in the shelter in the yard," said Sgt. Gary Knight. "She went in there to seek refuge and it was like a river running down on that storm shelter. It began to fill up with water and she appears to have drowned."
Among those injured, five people were seriously hurt in Oklahoma City and were taken to local hospitals, according to the Emergency Medical Services Authority.
The twisters severely damaged an Oklahoma City hotel and an RV park in the area. The most significant damage in the city was reported near Interstate 35, officials said. About 8,000 homes were left without power.
The city also issued its first-ever flash-flood emergency following a record 7.1 inches of rain, the National Weather Service said. The previous record for May 6 was 2.61 inches.
Heavy rains and flooding also damaged a terminal at Will Rogers World Airport, but the flooding is not expected to have a major effect on operations.
Forrest Mitchell, observations program leader for the National Weather Service's office in Norman, Okla., said much of western Oklahoma was at risk for more severe weather Thursday including thunderstorms.
"We could have hail as big as golf balls and could have winds up to 70 mph and possibly a few tornadoes," he said. "Along with that will be a rise of additional flash flooding."
The southern half of Kansas and eastern Colorado are also at risk, Mitchell said.