Tornado Alley

Tornado Alley, also known as Tornado Valley, is a loosely defined location of the central United States 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, Louisiana, Oklahoma, Kansas, South Dakota, Iowa and Nebraska. Tornado climatologists distinguish peaks in activity in certain areas and storm chasers have long recognized the Great Plains tornado belt.

As a colloquial term, there are no definitively set boundaries of Tornado Alley. The area common to most definitions extends from Arkansas, Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, Montana, Nebraska, North Dakota, Ohio, Oklahoma, South Dakota, Texas, Wisconsin, and eastern portions of Colorado, New Mexico and Wyoming. Research suggests that the main alley may be shifting eastward away from the Great Plains. Tornadoes are also becoming more frequent in the northern and eastern parts of Tornado Alley, reaching the Canadian Prairies, Ohio, Michigan, and Southern Ontario.

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.

Illinois, Wisconsin, Minnesota, Indiana, Michigan, and western Ohio are sometimes included in Tornado Alley. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian Prairies.

Tornadoes occur most frequently in the United States, particularly in the Central states, between the Rocky Mountains to the west and Appalachian Mountains to the east. Texas has the most overall number of tornadoes of any state. Per data collected through 2007, Kansas and Oklahoma ranked first and second respectively in the number of tornadoes per area. However, in 2013 statistics from the National Climatic Data Center reported Florida ranked first in tornadoes per area, although Florida is not a part of Tornado Alley. Florida's high ranking on the tornado list also has to do with the fact that the state sees a high number of waterspouts, small tornadoes that form over water. Although strong land-tornadoes have hit Florida and reports show Florida has a very high number of overall tornadoes, the tornadoes in the state seldom reach the velocity of those that may occur in the Southern Plains. In the United States, tornadoes typically occur in late spring and early summer during the changing season patterns as a warm air mass typically collides with a cold air mass resulting in tornadoes.

Another criterion for the location of Tornado Alley can be where the strongest tornadoes occur more frequently.

Tornado Alley can also be defined as an area reaching from central Texas to the Canadian Prairies and from eastern Colorado to western Ohio.