As night fell there were tornado warnings in Oklahoma and Texas while states like Kansas and Kentucky were getting blasted by thunderstorms, radar showed. A flash flood warning has also been put in effect for western parts of Kansas City through early Wednesday morning.
At least one tornado was confirmed spotted in Texas -- north of Dallas in Grayson County, according to the National Weather Service.
Matthew Day, a meteorologist with the National Weather Service office in Norman, Oklahoma, told CNN there were two circulations in northeast Oklahoma City, but the darkness prevented spotters from confirming if either was a tornado.
Police officers were headed to the area to help assess the damage, said Christie Yeager, a spokeswoman for the Oklahoma City emergency management office.
"The storm pushed through most of the city and touched down towards the very edge of the city. That's the good news," she said. There weren't yet reports of damage.
Earlier, the National Weather Service said one tornado had been spotted Tuesday night about 25 miles west of Bloomington, Indiana, and another was seen to the south in Vanderburgh County.
Amy Mangold with Evansville Emergency Management said there were no reports of injuries but there were initial descriptions of trees down and poles that had fallen on buildings.
In Kansas, the weather service's office in Wichita said Tuesday evening that there were several reports of hail bigger than golf balls.
One resident of the city posted a photo of a piece of hail almost as big as her palm.
A woman who lives just south of Wichita posted an Instagram video showing hail coming down, saying: "Our back room outside is starting to flood."
At the airport in Cincinnati, Ohio, passenger Leah Wilmington had to sit on a plane as torrential rain prevented her departure.
"Hmm I think I'm going to miss my connection...," she wrote, the rain so heavy it was difficult to see the planes at nearby gates.
At least two Oklahoma school districts decided the threat was significant enough to shut down for the day. Others opted to dismiss early, citing the threat of severe weather.
Be prepared
Forecasters advised people in the storm-threatened areas to prepare.
"Make sure you have a severe weather plan for you and your family," Bunting said. "If you don't, today is the day to develop it."
Among his tips ahead of the storms:
• Know where to seek shelter in your home or building.
• Have a way to get in touch with family or friends, or set a designated meeting point, to let them know you're OK after the storm.
CNN's Keith Allen, Rachel Aissen, Melissa Gray and Michael Pearson contributed to this report
