It is important to have a plan of action in the event a tornado threatens your family, and to rehearse that plan frequently. Such a plan should include what you and your family should do when at home, work, school, or outdoors. The time spent planning now could determine whether or not you survive a tornado.
First, know the county in which you live. Severe weather warnings are issued for counties, or for portions of counties. By keeping a highway roadmap nearby, you can follow storm movements, and better determine if you are threatened.
Have a NOAA Weather Radio handy at all times. Make sure your model has an tone-alarm feture, which will activate the radio when warnings or watches are issued for your area. If you are planning to be outdoors for an extended period of time, keep up with the latest weather information from your local National Weather Service office.
If you see a tornado, or hear that the National Weather Service has issued a Tornado Warning for your location...
Know Where to Go
In a home or a building, move to a pre-designated shelter, preferably the basement or the lowest floor of your home. Don't worry about opening your windows first - that would be a mistake, just get to the basement, and get under a sturdy piece of furniture or workbench. Grab blankets to cover yourself with, which will protect you from flying debris.
If an underground shelter (basement) is not available, move to an interior room or hallway on the lowest floor, and crouch down close to the floor. Again, grab extra blankets to protect yourself from flying debris. Stay away from windows - as they can shatter due to flying debris and the force of the wind.
If you are in a mobile home: Immediately move to a substantial shelter.
If you are caught outdoors and cannot get to a safe building. As a last resort, you should:
Immediately get into a vehicle, buckle your seat belt and try to drive to the closest sturdy shelter.
If your vehicle is hit by flying debris while you are driving, pull over and park.
Stay in the car with the seat belt on. Put your head down below the windows; cover your head with your hands and a blanket, coat or other cushion if possible.
If you can safely get noticeably lower than the level of the roadway, leave your car and lie in that area, covering your head with your hands. Your choice of whether to stay in your car should be driven by your specific circumstances. Your best choice remains getting to a secure building with a basement or saferoom.
If you find yourself outside or in a car with a tornado approaching and you are unable to get to a safe shelter, you remain at risk whether you stay in your car or seek shelter in a depression or ditch, both of which are last resort options that provide little protection. The safest place to be is in an underground shelter, basement or safe room.
Frequently Asked Tornado Questions (link to the NWS Storm Prediction Center).
Local Tornado Historical Climatology