Throw a extra cement block on top and forget it.
Tornados are actually very narrow bands, a mile away and you might just get a darkend sky,
most damage is in a band 200-800 ft wide, it can travel on the ground for miles, or hop-scotch across the earth, sometimes seting down once or twice and disappearing.
Best bet is don't get uptite, watch the sky, and head for the basement, if high winds develope, not really much else you can do.
Living on the I-44 tornado alley