Oklahoma's medical examiner's office says the tornado outbreak in the Oklahoma City suburbs killed five people. At least 89 people are believed injured.
Officials with the Oklahoma City Police Department confirmed to ABC News the body of a 4-year-old girl was recovered after she was swept away by flood waters. A family with several children was caught in the storm. They sought shelter in a ditch that rapidly filled with water, and several children were swept away. Authorities are looking out for two or three more children, all of whom are 4-years-old or younger.
A number of tornadoes touched down west and southeast of Oklahoma City during the Friday afternoon rush hour. Hospitals in the area say dozens of people were hurt, five critically.
As of 3:15 a.m. ET, Oklahoma Gas and Electric reported 84,177 customers were without power system-wide, and 82,590 customers were without power in the metro Oklahoma City area.
The broad storm hit during the evening rush hour, causing havoc on Interstate 40, a major artery connecting suburbs east and west of the city. To the south, winds approaching 80 mph were forecast for Moore, where a top-of-the-scale EF5 tornado killed 24 on May 20.
Floodwaters up to 4 feet deep hampered rescue attempts and frequent lightning roiled the skies well after the main threat had passed to the east.
Drivers were advised not to travel on Interstate 40 or Interstate 35. Downed power lines were across I-40. State troopers are being told to push the vehicles off the interstate to clear the roadway. There are literally not enough wrecker services and troopers to respond to all the car crashes.
Oklahoma Highway Patrol Trooper Betsy Randolph said troopers found the bodies of a woman and an infant near their vehicle. Randolph said it's not known if the woman was driving into the storm when it hit around 7 p.m. Friday.
Hail and heavy rain pelted the metro area to the point that emergency workers had trouble responding to "widespread" reports of injuries.
"We're scrambling around," said Lara O'Leary, a spokeswoman for the local ambulance agency. "There is very low visibility with the heavy rain ... so we're having trouble getting around.
"The damage is very, very widespread."
Standing water was several feet deep, and downtown Oklahoma City looked more like a hurricane had gone through than a tornado.
Tornado warnings were also posted Friday night near Tulsa and near St. Louis.
In Oklahoma, storm chasers with cameras in their cars transmitted video showing a number of funnels dropping from the supercell thunderstorm as it passed south of El Reno and into Oklahoma City just south of downtown. Police urged motorists to leave I-40 and seek a safe place.
"I'm in a car running from the tornado," said Amy Sharp, who last week pulled her fourth-grade daughter from the Plaza Towers Elementary School as a storm approached with 210 mph winds. "I'm in Norman and it just hit Yukon where I was staying" since last week's storm.
"I'm with my children who wanted their mother out of that town," Sharp said, her voice quivering with emotion.
At Will Rogers World Airport southwest of Oklahoma City, passengers were directed into underground tunnels and inbound and outbound flights were canceled.
Television cameras showed debris falling from the sky and power transformers being knocked out by high winds.
As the storm bore down on suburban Oklahoma City, Adrian Lillard, 28, of The Village, went to the basement of her mother's office building with a friend, her nieces, nephews and two dogs.
"My brother's house was in Moore, so it makes you take more immediate action," Lillard said while her young nieces played on a blanket on the floor of the parking garage. "We brought toys and snacks to try our best to keep them comfortable."
Well before Oklahoma's first thunderstorms fired up at late afternoon, the Storm Prediction Center in Norman was already forecasting a violent evening. From the Texas border to near Joplin, Mo., residents were told to keep an eye to the sky and an ear out for sirens.
Forecasters warned of a "particularly dangerous situation," with ominous language about strong tornadoes and hail the size of grapefruits - 4 inches in diameter.
Flash flooding and tornadoes killed three people in Arkansas late Thursday and early Friday. Three others were missing in floods that followed 6 inches of rain in the rugged Ouachita Mountains near Y City, 125 miles west of Little Rock.
This spring's tornado season got a late start, with unusually cool weather keeping funnel clouds at bay until mid-May. The season usually starts in March and then ramps up for the next couple of months.
Most tornadoes in the United States are relatively small. Of the 60 EF5 tornadoes to hit since 1950, Oklahoma and Alabama have been hit the most - seven times each.
ABC News and The Associated Press contributed to this report.