The following is an except from my campground report about the Buckhorn Campground at Lake of the Arbuckles in the Chickasaw National Recreation Area near Sulphur, OK. If you're interested in the full report it's on my blog here
I chose to stop here because Oklahoma was on the list of states I needed to visit in order to visit all 50, it was on my way to the southeast, it's more natural setting than private RV parks, and with a Senior Pass was but $12 a night including water, electricity and showers. The timing of my arrival, March, was still early enough in the year so as not to be overly concerned about tornados--being overly concerned is something at which I excel. The average number of twisters in OK in March is 5. In April it jumps to 11 and in May the average is 28 before tapering off in June to 7. This data is based on 1991 thru 2010.