Tornadoes, especially powerful ones, don't hit big cities very often. Between 2004 and 2014, major metropolitan areas were spared from tornadoes rated EF3 or above on the Fujita scale [source: Linkin et al.]. So is there something to the idea that urban landscapes somehow discourage tornadoes?
Unfortunately for city-dwellers, the answer is no. While it might seem logical that those tall skyscrapers are big enough to disrupt an approaching tornado, it turns out they aren't even close. Take Chicago's Willis Tower, which stands at nearly 1,500 feet (457 meters). That's less than 6 percent the height of a tornado, which can reach 5 to 10 miles (8 to 16 kilometers) into the sky. If anything, the urban landscape might actually help intensify thunderstorms into tornadoes. One study found that the heat stored in urban building materials may have actually contributed to the formation of an Atlanta twister in 2008 [source: Keim].
So why don't powerful tornadoes strike big cities more often? It's simple probability. Urban areas — even the sprawling ones — make up just a small fraction of the total land area. Chances are slim that any tornado will hit one of these densely populated places, much less the most powerful tornadoes. But it has happened in the past and will again in the future. And when it does, it could be devastating: One report suggests that a violent tornado in Chicago could inflict as much as $20 billion in damage [source: Linkin et al.]