THE midsection of the United States has been the world's hotspot for tornadoes for as long as anyone can remember. The term 'Tornado Alley' was coined in 1952 in a US Air Force research paper on severe weather in Texas and Oklahoma, but the unique frequency of tornadoes in the region is acknowledged even in Native American lore going back centuries. Tornado Alley mainly comprises the states of Texas, Oklahoma, Kansas and Nebraska, as well as parts of Colorado, the Dakotas, Missouri, Iowa and Minnesota. Tornadoes can and do occur in other places, but more of them happen in this part of the world than anywhere else.

Except, in the past decade or so, tornadoes have been occurring less frequently in the historic Tornado Alley and more frequently in places where tornadoes have been practically unheard of, such as West Virginia, Pennsylvania and New Jersey. There has also been a sharp increase in the number of tornadoes and severe storms capable of causing tornadoes in the southern states, Mississippi, Alabama, Georgia and Tennessee, leading some meteorologists to dub that part of the country 'Dixie Alley.'