Tornado Alley

Tornado Alley is a colloquial term for the area of the United States (or by some definitions extending into Canada) where tornadoes are most frequent. The term was first used in 1952 as the title of a research project to study severe weather in areas of Texas, Oklahoma, Kansas, South Dakota, Iowa, Illinois, Missouri, New Mexico, Colorado, North Dakota, and Minnesota. It is largely a media-driven term although tornado climatologists distinguish peaks in activity in certain areas and storm chasers have long recognized the Great Plains tornado belt.

Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Oklahoma, Kansas, into Nebraska. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies.

Active tornado regions have also been discovered in other areas of the world, such as in parts of Europe and especially in the Pampas lowlands of Argentina extending into adjacent areas of Paraguay and extreme southern Brazil. The Pampas has a high consistency of tornadoes, whereas Bangladesh and adjacent East India have the highest frequency of violent tornadoes outside the central and southern United States.

Over the years, the location(s) of Tornado Alley have not been clearly defined. No definition of tornado alley has ever been officially designated by the National Weather Service (NWS). Thus, differences in location are the result of the different criteria used.

According to the National Severe Storms Laboratory (NSSL) FAQ, "Tornado Alley" is a term used by the media as a reference to areas that have higher numbers of tornadoes. A study of 1921–1995 tornadoes concluded almost one-fourth of all significant tornadoes occur in this area.

...
Wikipedia