Tornadoes can occur everywhere in the world, from Spain to Wales and from Japan to the USA. But they mostly occur in the United States.
Tornadoes have hit al fifty states of the United States, but the 30-year average number of tornadoes per year in Alaska is closer to zero than to one. In Oklahoma though the average jumps to 52. Although no state is immune for tornadoes, there is an area that suffers from more tornadoes than any other. This area is called Tornado Alley. It is stretched out from West-Texas to North-Dakota. That is 1600 kilometres from north to south and 950 kilometres from east to west. Because it is not an official area the areas that are counted for can vary. What is certain is that large pieces of Texas, Kansas and Nebraska are a part of it. These areas suffer from more tornadoes than any other state in the United States.
The reason that this rather large area is hit more than any other areas is because in this area the circumstances are ideal. The terrain is relatively flat. Because of this the warm humid air going north from the gulf of Mexico and the cool dry air going south from Canada can easily crash into each other and create large super cells (also see sub-division development).
Texas is struck most of all in the last 50 years. From 1950 until now they suffered from almost 5500 tornadoes. That's is an average of 110 each year.
The 3rd and 4th of April 1974 will always be remembered. In 16 hours there were measured 148 tornadoes in 13 states. The tornadoes were varying from F0 to F5 (see subdivision scale).) and some of them traveled 60 kilometers. This was the biggest breakout ever. There were 330 people killed en almost 5500 people injured. Such a strike of nature is rare, but the scientist can assure us that it will come back. We know one thing for sure: there won't be so many people killed or injured, because of the better warning system.
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