Major flooding overwhelmed the metro area, stranding people in vehicles throughout the city. Baseball-sized hail pounded El Reno, breaking windows and destroying roofs.
More than 86,000 Oklahoma homes and businesses lost power.
Amy Elliott, a spokeswoman for the state medical examiner's office, confirmed that at least five people were killed in the storm, including a mother and child.
Canadian County Sheriff Randall Edwards said deputies were searching for a missing person, as well.
At least 87 people were treated for injuries at area hospitals.
Multiple injuries were reported near Interstate 40 and Banner Road, where six tractor-trailers were flipped on their sides near a westbound weigh station along the interstate between Yukon and El Reno.
Two other tractor-trailers overturned on the interstate — one blocking an eastbound lane and the other a westbound lane. Sheet metal debris littered the median.
“We are trying to get there, but hurricane-force winds and low visibility are preventing us from getting there,” Lara O'Leary, spokeswoman for the Emergency Management Services Authority ambulance service, said early Friday evening.
Keith Williams, 25, of El Reno took shelter in his car under the I-40 overpass at Banner Road as the tornado passed over.
“I got picked up twice and dropped,” he said, adding that his front tire got blown out and the back end of his car was smashed.
Williams said he then crawled in a vehicle with a television storm chaser and watched the tornado roar away.
“It was like a cotton candy machine. It kept picking things up and getting bigger,” Williams said. “The movie twister had nothing on this.”
Williams said he watched as a semi got sucked up under the overpass and dropped.
“It looked like spaghetti being sucked up,” he said.
Marcus Jolly, 32, of El Reno said he pulled off I-40 at a church where hundreds of people were gathered.
“It was a war zone,” he said of the area along I-40. “There were semis turned over and skeletons of buildings remaining.”
Rebecca Wear said she took shelter at a dry cleaners, and the owner took her to her home where they weathered the storm under a mattress in the hallway with other family members.
The Canadian Valley Technology Center, east of El Reno on U.S. 66, was heavily damaged. Instructor Tony Huffines, 57, said he and 12 students in a cartridge loading class took shelter in a basement.
“We were downstairs and saw a big, black cloud of debris out the only window that we could see,” Huffines said. “Everything went black. Our ears started popping. It went over us for 10 to 15 minutes and blew out skylights, all of the windows, blew down doors, tore down roofs, spun cars upside down and planted them on their sides in the road ditch.”
Huffines said when students finally were able to climb back upstairs, they saw airplanes from the center's aviation maintenance technology program strewn about.
“We were down underground and when we came up there were airplanes thrown around, trees without a limb left on them -- it's bad. But, nobody was hurt. I'm happy everyone got out of it,” he said.
“It's ugly,” Jim Meadows, owner of Don Serapio's, a Mexican restaurant in El Reno, said of conditions in that city. “There's a lot of poles down. There's a lot of houses blown away.”
Also damaged along U.S. 66 was the Gary E. Miller Canadian County Children's Justice Center and the OKC West Livestock Market, where cattle are auctioned, he said.
His restaurant had some rain leaks but will be open Saturday to feed emergency workers for free, Meadows said.
Behind his business, some of the roof was peeled off a shopping center that had been renovated into a meeting place, he said.
None of the children in detention at the justice center or in drug and alcohol treatment program there were hurt, Canadian County Associate District Judge Bob Hughey said.
“The roof has been damaged. There is a significant amount of water in the building,” the judge said. “All the kids are safe. All the kids are fine.”
In Moore, Mayor Glenn Lewis said the suburb was experiencing massive flooding and may have been hit again by a tornado. “There's damage all over. I've seen really big trees in the road and a couple of power lines. The power is completely out,” he said. “The water is about 4 feet deep in every end of town just about. We're advising people to stay off the roads and please don't get out in this. It's terrible.”
The mayor said he saw three ambulances headed to the area hit by a tornado May 20. He said he and his wife sought safety Friday night in the vault of his jewelry store.
Shell Food Plaza at I-40 and Banner Road also was heavily damaged, but employees took shelter in a nearby cellar and nobody was hurt at that location.
A tornado hit us,” said owner Ron Ulloa. “We lost a lot of glass, our roof is gone, and the building is totaled.”
Ulloa, who was not at the store when it was damaged, said two employees escaped injury by fleeing a block to a storm cellar, but passing motorists broke into the locked store seeking shelter as the tornado bore down. They were injured.
Store clerk Deana Ritchards, 35, said, “Four or five were injured. One cut himself on glass. The most serious was a broken leg. We saw the tornado in a pasture taking out some barns. It was huge.”
Torrential rains caused massive flooding in central Oklahoma, including downtown Oklahoma City. The Mesonet was reporting 4.61 inches of rain fell near El Reno and 3.21 inches fell in north Oklahoma City during a three-hour period Friday evening.