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It is a common myth that cities are safe from tornadoes, spawned from the fact that we mostly see tornado damage in small towns and suburbs here in the U.S. The answer to this question can be found by looking at any map of the U.S. or looking out the window while flying. The area of the U.S. covered by cities is very small compared to the area covered by farmland, suburbs, and small towns. Hence, the odds of a tornado striking a major city are very small compared to one hitting a small town.

The Center for Severe Weather Research at the National Center for Atmospheric Research reached the same conclusion. In the U.S., the area known as Tornado alley stretches from Colorado and Wyoming in the west to Ohio in the east, North Dakota in the north to Texas and Louisiana in the South (see map here). There are roughly two dozen major metropolises in this area, but they make up only a small fraction (less than 1%) of the total area. Thus, it is more likely a tornado will strike an area that does not contain a major city.

Dr. Fujita at the University of Chicago (for whom the tornado intensity scale is named) suggested that urban heat island effects may have an impact on small tornadoes. His thinking was that the increased heat levels in the center of major metropolises may disrupt the formation of small tornadoes (which make up the majority of tornado strikes). This assertion has not been proven or disproven and weather researchers continue to investigate the impact of cities on tornado formation.