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This article says, “While tornadoes are most common on the Great Plains and throughout the Mississippi River valley, they can occur almost anywhere in the United States.” Are tornadoes unique or more common in North America than elsewhere?

Ruth Housman
Newton Center, Mass.

Tornadoes have been spotted on every continent except Antarctica, says Harold Brooks of the National Severe Storms Laboratory in Norman, Okla. Most other nations haven’t been tracking twisters as long as the United States has, and their records are much less thorough, he notes. Despite those limitations, evidence suggests that a significant majority of tornadoes occurs in the continental United States, even though the lower 48 states occupy only about 5 percent of the world’s land area. –S. Perkins