One time we've camped with a thunderstorm warning in the area, we took the poles out of the tent, and laid our bikes on top. We didn't want our tent shredded by the wind. We went somewhere drier for the day. Another time we camped in a breezy place, probably about 10-15 miles/hr, and the tent is still stretched out at the seams, and we made sure to orient the tent with the wind. One neighbor didn't stake their tent and it was flying all over the place, and another had parts collapsing from the wind pressure due to the design of the tent. Anything above 20mph we'd at least drop the tent poles.
Tornadoes can destroy people's houses, much less some flimsy fabric tent. I wouldn't even ride out a tornado in an RV. Have you seen the aftermath of tornadoes?!