The damage can be done before the storm even gets here.
Dad and I were on the second story of my parents' house, glued to the Weather Channel and watching the path of a storm that was due to hit in 7 to 10 minutes. The fact that storms can be tracked so closely, that weather experts can tell exactly when and where it will be, still mystifies me. On this day, the storm trackers were right: The storm itself was still a few minutes away.
Dad finished saying "I think it's time to go downstairs," when the sound of destruction hit the side of the house. Later, when the storm had passed, we learned that the major storm damage in our area came from this 10-second burst of wind, long before the storm made it to us. My parents were lucky; they lost some tiles from the roof and a few lawn chairs (that they found across the street in the neighbors yard).
Others in the surrounding neighborhoods lost a lot more: Sheds, trees, and one woman lost the roof of her house. It was as if a giant picked up the corner and folded it into a paper fan.
None of this was caused by a tornado. We had been struck by a downburst, and the chaos was called "straight-line wind."
For more information on what straight-line winds are and how to prepare for them, please see this article.