The term ‘Tornado Alley’ has been used for quite some time by the media to describe an area of the contiguous United States that is known for frequent tornado activity. While most states experience tornadoes, the states and areas included in Tornado Alley receive somewhere around ninety percent of all recorded tornadoes in the country per year. The United States also has more tornadoes per year than any other country and reports more occurrences of violent tornadoes as well. Most tornadoes in Tornado Alley occur in late spring to early summer.
The area of Tornado Alley is primarily in the central United States, between the Appalachian Mountains and the Rocky Mountains. States that are almost entirely located within Tornado Alley, and are affected by frequent tornadoes, include: Texas, Oklahoma, Nebraska, Kansas, South Dakota, North Dakota, Iowa, and Minnesota. Other states that are partially affected include: Wyoming, Colorado, New Mexico, and Missouri.
In addition, some other areas and states in the Unites States are noted for having higher than average numbers of tornadoes per year but are not part of Tornado Alley. These include: Ohio valley area, Southern Michigan to Northern Illinois, the lower Mississippi Valley, the Tennessee Valley and the state of Florida. They all receive more tornadoes per year than surrounding areas but are varying distances away from what is considered to be Tornado Alley.
Of all the states included in Tornado Alley, Texas reports the most tornadoes of any other state in and is followed by Kansas and Oklahoma. It is possible that because of the size of Texas, the other two states might receive a higher number of tornadoes per square mile than the much larger Texas. In any case, the area of Northern Texas, all of Oklahoma and Kansas, as well as eastern South Dakota are considered to be the core of Tornado Alley.
Now that you know where Tornado Alley is, it’s time to talk about what creates this phenomenon. The effect of Tornado Alley is created by the movement of air across the United States. Cold, dry air from Canada and the Rocky Mountains moves south and east respectively, while warm, moist air from the Gulf of Mexico moves north. The convergence of these patterns creates an area of intense thunderstorms that are the ideal conditions for tornadoes to form. These intense rotating storms are referred to as supercells and under the right conditions; one or multiple tornadoes can form from them.