London, Ky. — More tornadoes plowed through the central U.S. on Monday, ripping apart buildings and knocking out power as people from Texas to Kentucky continued to clean up from days of severe weather that killed more than two dozen people and destroyed thousands of homes and buildings.

Much of the state, including Oklahoma City, Stillwater, Ardmore, and Ada, is expected to experience a moderate risk of tornadoes, which is the second-highest severity. Storms could produce softball-sized hail and wind speeds could top 80 mph,

It's been 12 years since the historic, deadly Moore, Oklahoma, EF5 tornado. New research has given light as to why no U.S. tornado has achieved an EF5 rating since.

Strong storms moved across Oklahoma on Monday, bringing hail and tornadoes to parts of the Sooner State. The severe weather prompted multiple tornado warnings throughout the state and a radar-confirmed tornado near Allen, Atwood and Calvin. There also was a tornado reported in Blanco, which is an unincorporated rural community in Pittsburg County.

The NWS confirmed a tornado struck southwest of Arnett. Residents were warned to take shelter. The agency said "risk for tornadoes and extremely large (3+) inch hail continues north and east of Harmon." Tornado warnings also have been issued for the towns of Sharon and Harmon until 7 p.m. May 18.

Breaking: Sequoya Quinton reports live sighting of a large tornado near Kiowa power plant. Caution advised in the area. Live updates.

Oklahoma may see an outbreak of severe storms with a chance of tornadoes and hail on Monday after multiple twisters touched down over the weekend.

Millions of people in the Midwest and Great Plains are in the path of numerous severe thunderstorms expected on Monday. Kansas City is expecting winds up to 50 MPH and half-dollar-sized hail that could damage roofs or cars.

Experts say planning before a tornado threatens is key for staying safe. Weather radios, basements and bicycle helmets can all help save lives.