While storms were still breaking out from the Midwest into the Appalachian Mountains region, the threat of more tornadoes had declined, meteorologists said.
The sixth Oklahoma victim was flown to a Texas hospital for treatment after the tornado struck the northwest Oklahoma town of Woodward early Sunday, said Amy Elliott, spokeswoman for the Oklahoma Medical Examiner's Office.
Three young girls and two other adults were also killed in the Woodward tornado, Elliott said.
More than 120 tornadoes were reported in the outbreak late on Saturday through early Sunday, which mainly hit less-populated areas of Kansas and Oklahoma, said Henry Margusity, an AccuWeather.com senior meteorologist.
The storms skipped through what is often called "Tornado Alley" in the U.S. Central and Southern Plains, but mostly struck rural areas, sparing the region from worse damage.