FACTBOX-Some facts about tornadoes

March 1 (Reuters) - Tornadoes ripped through the Southern and Midwestern United States on Thursday, killing at least 19 people.

Following are some facts about tornadoes:

-- Tornadoes are one of nature's most violent storms. In an average year, about 1,000 tornadoes are reported across the United States, resulting in 80 deaths and more than 1,500 injuries.

-- A tornado is a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph (400 kph) or more. Damage paths can be in excess of one mile (1.6 km) wide and 50 miles (80 km) long.

-- Tornadoes come in all shapes and sizes and can occur anywhere in the United States at any time of the year. In the southern states, peak tornado season is March through May, while peak months in the northern states are during the summer.

-- Because a tornado is part of a severe thunderstorm, and thunderstorms occur all over the Earth, tornadoes are not limited to any specific geographic location. Tornadoes have been documented in every one of the United States, and on every continent, except Antarctica (even there, a tornado occurrence is not impossible).

-- In terms of absolute tornado counts, the United States leads the list, with an average of over 1,000 tornadoes recorded each year. A distant second is Canada, with around 100 per year. Other locations that experience frequent tornado occurrences include northern Europe, western Asia, Bangladesh, Japan, Australia and New Zealand. Britain has more tornadoes, relative to its land area, than any other country. Most British tornadoes are relatively weak.

-- The deadliest tornado in the United States touched down on March, 18, 1925, killing 695 people and injuring 2,027 in Missouri, Illinois and Indiana. (Source: U.S. National Oceanic & Atmospheric Administration)