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The Debunker: Should You Crack Your Windows During a Hurricane or Tornado?

by Ken Jennings

Did you know that September is National Preparedness Month? The catchy government slogan is "Be disaster aware! Take action to prepare!" But how disaster-aware are we really? Lots of the things we know about life's worst calamities are actually wrong--and in some cases, dangerously so. Luckily, Ken Jennings, Jeopardy! survivor and professional know-it-all, is here to set us straight. Because what could be more disastrous than ignorance? Well, maybe a big volcano. Ignorance, and also a big volcano.

The Debunker: Should You Crack Your Windows During a Hurricane or Tornado?

You probably haven't heard of the National Wind Institute at Texas Tech University, but the lab has saved countless lives over the last fifty years with research into the effectiveness of tornado shelters and other types of storm preparedness. The heart of the lab: a pneumatic cannon that can simulate wind and flying debris at speeds up over 250 miles per hour. If your ground shelter doesn't withstand TTU's wind lab, it's back to the drawing board for you.


In a series of 1977 tests, engineers at Texas Tech took on the popular notion that it's a good idea to crack or open windows when a big storm's a-comin'. Storms are often accompanied by big pressure drops, the theory goes. What if the sudden pressure differential between indoors and outdoors is what causes houses to splinter and roofs to go flying?

Spoilers: it's not. We now know that the largest pressure drop in a tornado is no more than 10 percent, which a structure can equalize in seconds whether windows are closed or not. Simulations reveal that opening windows isn't just a waste of precious time--it's actively harmful. Wind gusts that enter a house through an open window have to get out somehow, often by pushing roofs upward or walls out. (That's aside from any damage caused by debris blowing in from the outside.) The National Hurricane Center says that a masking tape 'X' on your windows-- official government advice until the 1980s --is equally useless. Unless you have hurricane shutters, the best thing you can do with your windows in a storm is to get the hell away from them.

Quick Quiz: Who was Oscar-nominated in 2000 for playing the title role in the movie The Hurricane?

Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.