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.
Tornadoes in the United States
Most tornadoes in the United States occur east of the Rocky Mountains. The Great Plains, the Midwest, the Mississippi Valley and the southern United States are all areas that are vulnerable to tornadoes. They are relatively rare west of the Rockies and are also less frequent in the northeastern states. Tornado Alley is a colloquial term for an area particularly prone to tornadoes. There is no officially defined 'Tornado Alley' – at its broadest this area stretches from northern Texas to Canada with its core centered on Oklahoma, Kansas and northern Texas. Another highly significant region – colloquially known as Dixie Alley – is the southern United States and particularly the northern and central parts of Alabama and Mississippi. Florida is one of the most tornado-prone states. However, Florida tornadoes only rarely approach the strength of those that occur elsewhere.