What is considered to be “tornado alley”?

Dear Tom,
What is considered to be “tornado alley”?
Gregory Allenson
Dear Gregory,
“Tornado alley” is one of those terms that means something different to each of us. Meteorologically, it refers to that portion of the United States across which tornadoes occur most frequently, encompassing the Great Plains area between the Rocky Mountains on the west and the lower and mid Mississippi River Valley on the east. Tornadoes reach their absolute maximum of occurrence across Nebraska, Kansas, Oklahoma and north Texas.
The United States leads the world in tornado production. About four of every five tornadoes that develop on the entire planet occur right here in the United States, and the majority of them form in the tornado alley defined above. However, it is important to note that tornadoes do occur outside tornado alley and have occurred in every state.

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