Packing winds of up to 300 mph, tornadoes are considered nature’s fiercest weather phenomena, a violently rotating column of air extending from a thunderstorm, the result of a collision of cold dry air and warm moist air. Tornadoes strike with little or no warning and can carve a groove of destruction a mile wide and 50 miles long.

Some facts about tornadoes:

  • While tornadoes have been documented on every continent except Antarctica, the great majority touches down east of the Rocky Mountains in the United States. The United States averages about 1,000 tornadoes each year, according to the National Climatic Data Center in Asheville, North Carolina. Canada is next with just 100 a year.
  • The south-central plains states that comprise “Tornado Alley” have a disproportionately high frequency of tornadoes. Tornado Alley includes parts of Texas, Oklahoma, Kansas, Nebraska, Colorado and South Dakota.
  • Florida also receives a high number of tornadoes because of frequent thunderstorms. Florida averaged 55 tornadoes a year from 1953-2004.
  • Texas averaged 139 tornadoes a year during that same period, the most in the country.
  • In the first 10 months of 2011, there have been 1,488 confirmed tornadoes – nearing the annual record of 1,817 set in 2004.
  • Tornadoes aren’t limited to flatlands. In July 2004, Scott Newton photographed a tornado at about 12,000 feet above sea level while hiking in Sequoia National Park in California.
  • April 2011 was a record month for tornadoes in the United States with 753 tornadoes that killed more than 360 people, according to the National Oceanic and Atmospheric Administration.
  • Tornadoes cause an average of 70-80 fatalities and 1,500 injuries in the U.S. each year.
  • The tornado that hit Joplin, Missouri on May 23, 2011 killed more than 150 people, making it the deadliest single tornado since modern recordkeeping began in 1950.
  • Tornadoes caused 45 deaths in the United States in 2010, the most recent year for which statistics are available.  Nearly half those victims – 42 percent – lived in mobile homes.
  • The "Tri-state" tornado of March 18, 1925 killed 695 people as it traveled more than 200 miles at 60-73 mph across parts of Missouri, Illinois and Indiana.
  • Tornadoes are most likely to touch down between 3 p.m. and 9 p.m. because most tornadoes are related to the strength of a thunderstorm, which gain power through the heating of the day.
  • Tornadoes can happen any time of year, but are most frequent in late spring and early summer when warm and cold air masses often clash. The tornado season varies from state to state. For example, in Texas, the months of peak tornado activity are April-June. In Florida, the season is May-July. In California, January-April.
  • Protect your family from tornadoes by buying a NOAA weather radio and keeping it on your nightstand. The radio will sound a loud alert when the National Weather Service issues a tornado warning for your area. This should give you time to gather your family in the basement or in an interior room such as the bathroom. If you’re in a mobile home, get out immediately and go to the lowest floor of a nearby building or a storm shelter.
  • The weather forecast of a “tornado watch” means the conditions are ripe for a tornado and you should be alert for approaching storms and stay tuned to NOAA Weather Radio, commercial radio or television for information. If officials issue a “tornado warning” that means a tornado has been sighted or indicated by weather radar and you should immediately take shelter.
Know of other tornado facts? Leave us a note in the comments below.

Related stories on tornadoes from MNN and partners:

10 ways to prepare for tornadoes, strong winds and hailstorms

9 things you don't know about tornadoes

Tornado myths debunked (by Allstate)