Heavy winds and dangerous amounts of rain have pounded Kansas, Nebraska, and Texas as well. The rain continued to fall Thursday, pushing some rivers and creeks up to or over their banks.
The storms and flooding "have caused extensive damage to public and private properties," Oklahoma Gov. Mary Fallin said in issuing an emergency declaration for 12 counties. The weather "threatens the lives and property of the people of this state and the public's peace, health and safety."
The counties are Alfalfa, Blaine, Caddo, Canadian, Cleveland, Dewey, Garfield, Grady, Grant, Major, McClain and Oklahoma. At least 30 people were reported injured in the storms, the state Department of Health said.
The good news: A second day of tornadoes appears unlikely, with the National Weather Service Storm Prediction Center
forecasting only a slight chance of powerful thunderstorms in the Great Plains and parts of Texas, including the Dallas area.
Hail in Cookietown
Severe thunderstorm watches
came and went in the early morning in southern Oklahoma and northern Texas. The weather service's Norman, Oklahoma, office reported a severe storm before dawn in the community of Cookietown with "hail the size of golf balls and very heavy rainfall."
Heavy rain in the spring in this part of the United States is hardly an anomaly. Nor is the flooding that often accompanies it.
Still, that doesn't make it any less of a serious challenge.
Authorities issued flash flood warnings for Thursday morning in southeastern Nebraska and Oklahoma, including Oklahoma City. Those aren't scheduled to last long, but some flood warnings -- tied to waterways set to rise even after the rain stops -- will remain in effect into the weekend.
The Big Blue River near Crete, Nebraska; the East Cache Creek near Walters, Oklahoma; and the Deep Red Creek near Randlett, Oklahoma, are expected to go past flood stage later Thursday. Turkey Creek, near Wilber, Nebraska, was already more than 5 feet above flood stage around 2:45 a.m. (3:45 a.m. ET) Thursday and projected to go even higher.
Similar problems persisted in other parts of Oklahoma. For example, the North Canadian River was 3 feet above flood stage just after midnight around Oklahoma City and projected to rise 2 feet more before finally cresting.
Texas and Louisiana also had their share of flooding headaches, including sections of the Neches River and the Mississippi River around Baton Rouge.
At least 13 hurt, 'debris just everywhere'
Many of these issues follow intense downpours on Wednesday, like the nearly 9 inches of rain in parts of Nebraska and 3 inches per hour that fell in pockets of north Texas.
Authorities in Oklahoma City, located in the middle of its namesake state, issued a flash flood emergency for the first time ever after 7-plus inches of rain fell there.
That city's Will Rogers World Airport
experienced flash flooding and water damage as the storm rolled through. But the prospect of tornadoes was an even bigger fear, promoting two evacuations of terminals -- the last of which began around 7 p.m. and lasted for nearly three hours.
One of those hit a mobile home park in Oklahoma City, injuring at least 13 people, according to Susie Patterson of that city's Emergency Medical Services Authority.
In north-central Kansas, reported tornadoes ripped apart homes, uprooted trees and downed power lines
, CNN affiliate KWCH reported. And Nebraska's Norman Regional Hospital went on generator power after suffering minor damage.
Even for those not directly in the line of suspected tornadoes, the storm left behind a mess.
"There's debris just everywhere, and there's a lot of water on the roadways," Capt. Paul Timmons of the Oklahoma Highway Patrol told CNN's "Erin Burnett OutFront."