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For the book by William S. Burroughs, see Tornado Alley (book).

Another book by the title "Tornado Alley: Monster Storms of the Great Plains" is written on the subject of tornadoes, tornado research, and storm chasing by prominent research meteorologist Howard Bluestein.

Yet another book by the title "Tornado Alley" deals with the topic in science fiction by William Tuning.

An outline of Tornado Alley in the United States, here defined as the area where approximately 1 day or greater per decade contained a significant tornado (source: NOAA)

Tornado Alley is a colloquial term most often used in reference to the area of the United States in which tornadoes are most frequent. It encompasses the great lowland areas of the Mississippi, the Ohio and lower Missouri River Valleys, as well as the Southeast. Although no state is entirely free of tornadoes, they are most frequent in the Plains area between the Rocky Mountains and Appalachians. Oklahoma, Kansas, Arkansas, Iowa, and Missouri are entirely within Tornado Alley, as well as Northeastern Texas, Eastern Colorado, Northern Louisiana, Central and Southern Minnesota, and South Dakota, Northwestern Mississippi, Central and Southern Illinois, Central and Southern Indiana, and parts of Central, southeast and southwest parts of Nebraska. Also small parts of far Western Tennessee and Kentucky are typically included as well as some parts of Wisconsin.

This region's abundance of tornadoes is made possible by the collision of cold fronts from Canada and warm fronts from the Gulf of Mexico.

In the heart of tornado alley, building codes are often stricter than those for other parts of the U.S., requiring strengthened roofs and more secure connections between the building and its foundation. Other common precautionary measures include the construction of storm cellars, and the installation of tornado sirens. Tornado awareness and media weather coverage are also high.

Tornado activity in the United States. The darker-colored areas denote the area commonly known as Tornado Alley.

Statistically, most U.S. tornadoes occur in Texas [1]. When land area is taken into account, however, Florida has the highest density of tornado occurrence in the country [2]. Nearly all of these tornadoes are weak and not produced by supercell thunderstorms; Oklahoma has the highest occurrence of such "classic" tornadoes. The time of year of highest tornado frequency, or "tornado season", shifts geographically throughout the year. In general, the tornado alley tends to shift farther north as the weather warms across the U.S. Technically speaking, however, the central plains may be considered part of the tornado alley almost all-year-round, since this is where "temperature swings" between warm and cold air are most common.

In contrast, the Northeast and West tend to be the least tornado-prone regions in the United States.

• List of tornadoes and tornado outbreaks