U.S. has world’s highest tornado risk. Here’s why.

Friday night’s cataclysmic quad-state tornado outbreak reminds us of the vulnerability of our country to tornadoes and how the threat of these destructive storms looms menacingly real over the eastern two-thirds of the United States during any season of the year.

We’re not alone, as tornadoes happen in other parts of the world, too. But by sheer numbers (about 1,200 on average per year), the United States has the dubious honor of residing at the top of the list.