What do you do in a tornado warning when in the RV?

We were in Iowa many years ago, in a small city central park, when there were tornado warnings. We asked where to go, and nobody could give us a good answer except one guy who summed it up a lot like they used to tell us in school if there was a nuclear strike or earth quake, which ended with some thing like, "put your head between your knees and kiss your gluteus maximus goodbye. :)