Tornado climatology
The United States averaged 1,274 tornadoes per year in the last decade. April 2011 saw the most tornadoes ever recorded for any month in the US National Weather Service's history, 875; the previous record was 542 in one month. It has more tornadoes yearly than any other country and reports more violent (F4 and F5) tornadoes than anywhere else.
Tornadoes in the United States
Although the period in which most tornadoes strike ("tornado season") is March through June, tornadoes – including violent tornadoes and major tornado outbreaks – have been documented in the United States during every month of the year. Two examples of this are when a series of tornadoes hit the state of Indiana on November 22, 1992, and injured at least nine people. Another notable non-season tornado was where a tornado struck the area of McLean County, Illinois. Even though the tornado was during a winter month, it blew 20 railroad cars off their tracks, and hauled a camper over 100 yards (91 m).