Tornado climatology
Tornadoes have been recorded on all continents except Antarctica and are most common in the middle latitudes where conditions are often favorable for convective storm development. The United States has the most tornadoes of any country, as well as the strongest and most violent tornadoes. A large portion of these tornadoes form in an area of the central United States popularly known as Tornado Alley. Other areas of the world that have frequent tornadoes include significant portions of Europe, South Africa, Philippines, Bangladesh, parts of Argentina, Uruguay, and southern and southeast Brazil, northern Mexico, New Zealand, and far eastern Asia.
Tornado records
The infamous 1974 Super Outbreak of April 3–4, 1974, which spawned 148 confirmed tornadoes across eastern North America, held the record for the most prolific tornado outbreak for many years. Not only did it produce an exceptional number of tornadoes, but it was also an inordinately intense outbreak producing dozens of large, long-track tornadoes, including 7 F5 and 23 F4 tornadoes. More significant tornadoes occurred within 24 hours than any other week in the tornado record. Due to a secular trend in tornado reporting, the 2011 and 1974 tornado counts are not directly comparable.