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.
Moore, Oklahoma
Moore itself has seen ten tornadoes between 1998 and 2015, three of them big enough to claim lives and cause catastrophic damage. The city of Moore was damaged by significant tornadoes on October 4, 1998; May 3, 1999; May 8, 2003; May 10, 2010; and May 20, 2013, with weaker tornadoes striking at other times, notably May 31, 2013 and March 25, 2015. Moore is located in Tornado Alley, a colloquial term for the area of the United States where tornadoes are most frequent. About 20 tornadoes occurred in the immediate vicinity of Moore from 1890 to 2013. The most significant tornadoes to hit Moore occurred in 1893, 1999, and 2013.