Tornadoes in the United States
The Midwestern states are very prone to tornado activity, as they are part of "Tornado Alley." States included in the area that are hit by tornadoes the most are Oklahoma, Kansas, Missouri, Nebraska, Iowa, and South Dakota. The Midwestern States are often hit by tornadoes during the late spring and early summer months, especially the months of May and June. This is due to the aforementioned air mass moving northward into the Midwest and combining with another air mass that move southward from Canada. This creates unstable air, creating the potential for storms to strike the most during these months. The frequency begins to decrease in the middle of the summer, as the air mass moves northward into the Great Lakes states.
Tornadoes in the United States
Nebraska is fifth overall for sheer numbers of tornadoes, while Indiana has had 88 violent tornado reports from the 1950–2006 period, more than any state except Oklahoma. Iowa reported 3,900 almost as many as Texas. The deadliest tornado in US history, the Tri-State Tornado, struck Missouri, Illinois, and Indiana in March 1925. St. Louis, Missouri and neighboring East St. Louis, Illinois have been hit more than once by violent tornadoes, the most notorious of which was the St. Louis Tornado of May 1896. The New Richmond Tornado of May 1899 and the Flint, Michigan tornado of June 1953 also rank amongst the deadliest tornadoes in US history. The region was badly hit by the Palm Sunday Tornado Outbreak in April 1965 and by the Super Outbreak of April 1974. According to NCDC figures for the 1950 to 2006 period, Nebraska reported 2,440 tornadoes followed by Iowa (2,185), Illinois (2,086), Missouri (1,922), South Dakota (1,487), Minnesota (1,477), Indiana (1,327), North Dakota (1,216), Wisconsin (1,185), Michigan (981), and Ohio (916).