The storms dropped baseball-sized hail in southwest Oklahoma on Saturday evening as an unstable air mass hung over the state, said meteorologist Ken Gallant with the weather service.
People reported golf ball- to baseball-sized hail in an area from Altus in Jackson County, up through Hobart in the adjacent Kiowa County, Gallant said.
People posed with palms full of large hail, and posted pictures to the Norman-based forecast office's Facebook page as the storms moved through the area.
Much of Oklahoma was under a tornado watch into the night Saturday.
The weather service reported a cluster of severe storms moving over Kiowa, Washita and Caddo counties about 7:45 p.m.
Storms with gusts between 45 and 50 mph had moved through Canadian County near El Reno about 8:15 p.m. Saturday.
Gallant warned that severe weather, including tornadoes, are a possibility with a large, unstable air mass over much of the state and advised that residents should monitor weather through the evening.
The weather service reported tornado outbreaks in Kansas and Nebraska as early as 6 p.m.