The twisters are part of a severe weather outbreak that is sweeping through the region as storms move east.
Baseball-sized hail, wind gusts and tornadoes are threatening to pummel parts of the central Plains and Midwest through Monday.
"We still have a couple of active cells, and so we don't know for sure that it's over yet," said Jerry Lojka with the Oklahoma Department of Emergency Management.
Beyond the Midwest, other areas saw severe weather on Sunday. In Atlanta, serious flooding was reported amid storms producing heavy rainfall.
Here's a quick look at CNN meteorologist Melissa Le Fevre's forecast for Monday for hard-hit Midwestern states:
The surface front may stall on Monday, leading to showers and thunderstorms through the day. Localized heavy rainfall may lead to the need for flood watches and warnings.
There is a threat for strong storms in the late afternoon. With the heavy rain that will occur through the weekend, flooding could become a problem Monday night.
Showers and storms are expected to develop on Monday afternoon. Large hail is possible and though the tornado threat looks low, it cannot be ruled out.
Flooding is expected to become an issue after localized heavy rainfall. Afternoon storms could produce large hail, damaging wind gusts and possible tornadoes. In St. Louis, storms will reorganize during the afternoon and evening hours. Threats include large hail, damaging winds and the possibility of tornadoes.