A tornado is defined as a violent 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 miles per hour or more. Damage paths can be in excess of one-mile wide and 50 miles long. Tornadoes may occur with little or no advance warning or siren activation.

Before the Storm

  • Locate an accessible basement or corridor location in your building. Stay informed through local media sources on days when severe weather is expected.
  • Obtain a National Oceanic and Atmospheric Administration (NOAA) Weather Radio with a warning alarm tone and battery backup to receive warnings, and keep a good reliable flashlight in your office/work area.
  • Contact the Department of Safety and Security at Purdue for more information about tornadoes.
  • The exterior warning sirens are tested at 11 a.m. on the first Saturday of every month except during periods of adverse weather conditions.

During the Storm (possible indicators of a tornado):

  • Dark, often greenish sky.
  • Large hail.Loud roar, similar to a train.
  • Cloud of debris (the tornado may not be visible).
  • Wind becomes calm and still.
  • Frequent lightning.
  • Tornadoes generally occur near the trailing edge of a storm.

When Taking Shelter

  • Proceed to the basement of any building that has a basement or subwalk. Position yourself in the safest portion of the area away from glass. Be prepared to kneel facing a wall and cover your head.
  • In high-rise buildings (four stories or more), vacate the top floors and move to a lower floor or to the basement. Position yourself in an interior corridor away from glass. Be prepared to kneel facing the wall and cover your head.
  • Occupants of wood-frame or brick buildings with wood floors should leave the building and go directly to a more substantial concrete building, preferably with a basement.

Warning Signals

  • Outdoor sirens will sound for a period in excess of two minutes. When this occurs, tune in to local radio and TV stations to determine the nature of the emergency. A voice message will be broadcast over WBAA, the University television antenna system, and other local radio and television stations. The "all clear" signal is announced by radio and television stations. The sirens remain silent.

Weather Terms

  • Severe thunderstorms: The National Weather Service issues severe thunderstorm watches and warnings. Remember that tornadoes are spawned from severe thunderstorms.
  • Tornado watch: A tornado watch is issued when atmospheric conditions are favorable for the formation of tornadoes in a given area. Stay informed by listening to radio or television.
  • Tornado warning: A tornado warning indicates that a tornado has been sighted and poses a definite threat to a given area.