Tornado Facts

Become more knowledgeable about tornados by reading our tornado facts.

Tornadoes form where warm moist air is trapped underneath a layer of cold, dry air. This instability is upset when the warm bottom layer gets pushed up — either by heating near the ground, or by an influx of cold air.

As the moist air rises, it cools, forming clouds and thunderstorms. If the conditions are right, the rapidly rising air will spin around a central funnel, at speeds sometimes exceeding 250 mph. A tornado technically is born when this funnel cloud touches down on the ground.

Tornadoes are most common between March and August, but can occur at any time. They can happen anywhere, but are most common in Arkansas, Iowa, Kansas, Louisiana, Minnesota, Nebraska, North Dakota, Ohio, Oklahoma, South Dakota, and Texas – an area commonly called “Tornado Alley.” They are most likely to occur between 3pm and 9pm but can occur at any time, even at night.

During a tornado, people face hazards from extremely high winds and risk being struck by flying and falling objects. Knowing what to do when you see a tornado, or hear a tornado warning, can help protect you and your family. It’s important all family members know what to do if a tornado watch and/or warning is issued for your area.

  1. Be Prepared: Take the time with your family to develop a tornado emergency plan. Ensure that all family members know where your storm shelter is located and how to properly shut and latch the door.
  2. Stay Tuned for Storm Watches and Warnings: When there are thunderstorms in your area, turn on your local radio or TV to get the latest emergency information. Listen for announcements of a tornado watch or tornado warning.
  3. Know your Local Warning System: Learn about your local tornado warning system. Most tornado-prone areas have a siren system. Know how to distinguish between the siren’s warnings for a tornado watch and a tornado warning.
  4. Know the difference between a Tornado Watch and a Tornado Warning: A tornado watch defines an area where tornadoes and other kinds of severe weather are likely in the next few hours. If you’re in such an area, be alert. A Tornado warning means that a tornado has been spotted or that radar has shown circulation in a storm that could spawn a tornado.

During a Tornado Watch

During a Tornado Warning

  • You should take shelter immediately!

The Fujita scale ranks tornado strength based on the damage they cause. The scale runs from EF0 to EF5. EF4 and above account for less than 1 percent of all tornadoes, but account for 70 percent of tornado-related deaths.

  • Up to 85 mph wind
  • Light damage
  • Chimneys are damaged, tree branches are broken, shallow-rooted trees are toppled
  • 86-110 mph wind
  • Moderate Damage
  • Roof surfaces are peeled off, windows are broken, some tree trunks are snapped, unanchored manufactured homes are over-turned, attached garages may be destroyed.
  • 111-135 mph wind
  • Considerable Damage
  • Roof structures are damaged, manufactured homes are destroyed, debris becomes airborne (missiles are generated), large trees are snapped or uprooted.
  • 136-165 mph wind
  • Severe damage
  • Roofs and some walls are torn from structures, some small buildings are destroyed, non-reinforced masonry buildings are destroyed, most trees in forest are uprooted.
  • 166-200
  • Devastating Damage
  • Well-constructed houses are destroyed, some structures are lifted from foundations and blown some distance, cars are blown some distance, large debris becomes airborne.
  • Over 200 mph wind
  • Incredible Damage
  • Strong frame houses are lifted from foundations, reinforced concrete structures are damaged, automobile-sized debris be-comes airborne, trees are completely debarked.