KATIE, Okla. – Severe storms claimed lives, destroyed homes and injured livestock across southern Oklahoma on Monday evening.
Shortly after 4 p.m., a tornado developed near Elmore City and continued east toward Wynnewood, leaving behind a trail of destruction.
Crews with the National Weather Service surveyed the damage on Tuesday morning to learn more about the storm.
However, on Wednesday the NWS upgraded the tornado to an EF-4.
"The May 9th Katie tornado is being upgraded to EF 4 based on more intensive review of survey data," the NWS said on Twitter.
Also on Wednesday, surveyors modified the tornado that hit Bromide to an EF-3.
The tornado that touched down in Payne County near Stillwater had a six-mile long path and was rated as an EF-2.
The National Weather Service says that the most intense damage they have found has been near the town of Katie, just west of I-35 and southwest of Wynnewood.
In all, seven tornadoes were confirmed from Monday evening.
The areas that were affected include Stillwater, Norman, Katie, Sulphur, Bromide, Atoka/Wapanucka and Bennington.