Why Does the United States Have So Many Tornadoes?

Last night, tornadoes ravaged Illinois, Indiana, and Alabama, leaving two dead and even more injured, marking a violent start to tornado season, which usually peaks in May. Unfortunately, tornado season is starting earlier and earlier each year, research shows, and the storms are only getting more powerful.

According to NOAA, the United States can expect to experience 1,200 tornadoes per year on average—an order of magnitude more than other countries. But why so many? It has to do with our country’s vast size and its unique geography.

Tornadoes are usually spawned from powerful supercell thunderstorms, which form when cold, dry air meets warm, humid air, causing powerful winds. In the United States, the cold, dry air either comes down from Canada in the north or the Rocky Mountains in the west, while warm, humid air bubbles up from the Gulf of Mexico or evaporates from plants in the Great Plains.

Read more: “What Sets Off Bomb Cyclones”

These flat grasslands provide an expansive playground for tumultuous winds, which is why the “Tornado Alley” states of South Dakota, Nebraska, Kansas, Oklahoma, and Texas are particularly conducive to twister formation. The lesser known “Dixie Alley”—spanning Louisiana, Arkansas, Tennessee, Mississippi, Alabama, and Georgia—is home to deadlier tornadoes, on the other hand.

But don’t these conditions exist in other places on Earth? They do. South America, for example, has its own tornado corridor, called “Pasillo de los Tornados.” There, a confluence of warm, humid air from the Amazon rainforest meets cold, dry air from the Andes Mountains over Argentina, Paraguay, Uruguay, and Brazil, creating powerful twisters.

However, because these areas aren’t as heavily populated, the tornadoes aren’t closely monitored and many likely slip through the cracks. Russia and Australia are in the same boat, with tornadoes spinning through sparsely populated areas that go unnoticed by storm trackers.

With climate change wreaking havoc on weather systems, other countries might be more inclined to step up their tornado monitoring efforts. But even if they do, it’s unlikely anyone will take the dubious honor of “most tornadoes” from the United States.