On June 15, 1990, Stillwater had a F3 tornado. There was one death. Don't think it was associated with a big outbreak.

The story here: https://stillwaterweather.com/1990tornado

On June 8, 1974, Drumright had a much worse tornado, F4, with 12 deaths. It was part of a large outbreak.

Bad June tornadoes are fairly rare, but not so rare that you can take your guard down.