I grew up in Oklahoma and live in North Texas now. Tornados are a fact of life. We don't get them daily, but we do know what to do if there is one in our area. The kids practice tornado drills in school (tuck, duck and cover). Most of the kids can identify wall clouds and know the direction a tornado is most likely to go.
We joke about hearing a tornado warning and grabbing the video camera to take up on the roof. Quite honestly, I have been 2 blocks away from two separate tornados before and had no damage. Straight-line winds have damaged our property however.
The National Weather Service Severe Storms lab is based in Norman, Oklahoma. They have the stormchasers who go out and shoot a lot of the video you see on TV. They also help develop the radar that can visualize the storms and is accurate to within a block. The emergency sirens are checked on a weekly basis - unless we are under an alert at that time.
Look up the May 3, 1999 tornado in Moore, Oklahoma. Rated an F5 under the old scale, it caused an unbelievable amount of damage. Several friends were left with the foundations of their homes - and nothing else.