When a tornado warning is issued, it means that a government agency believes that there is a serious risk of tornadoes, due to the weather conditions, or that tornadoes have been spotted in the area. The most important thing to do during a tornado warning is to take cover in a secure place, and to bring a radio along to listen for an all clear, which will indicate that the warning has been lifted. However, it helps to prepare ahead for tornado warnings, especially in areas of the world where this type of weather is common.
The best place to shelter during a tornado is in a basement or storm cellar. If such a space is not available, staying indoors in the center of a building is a good solution. People in cars, trailer homes, tents, and other unstable structures should exit and find a solid building to shelter in. If no indoor shelter is available, the best thing to do is to lie flat in a low area such as a ditch, taking care to watch out for flooding. Sheltering under bridges and overpasses may be popular in the movies, but it can be dangerous in real life, as these structures can collapse, and falling debris can hit people trying to take shelter.
At home, it's a good idea to have a tornado plan and to practice for it at least once a year so that people and pets can get to a shelter in a few minutes if necessary. The designated safe space for sheltering should be stocked with food, water, blankets, batteries, flashlights, and entertainment. It's also a good idea to remind people that flying debris is a big risk in a tornado, and that protective coverings such as blankets, tarps, or heavy jackets should be used to cushion the body while approaching a shelter when a tornado warning is issued.
Tornadoes can also be accompanied by severe thunderstorms, which carry some additional hazards. Heavy weather can cause power outages or block roads, which can become an issue if someone is injured, and such storms can also cause flooding or fires. During a tornado warning, people should be aware of these hazards, and the fact that the risk of thunderstorms can persist after a tornado warning is canceled or lifted.
A weather agency may also issue a tornado watch, which means that conditions are ripe for the formation of tornadoes, so people should be careful. Weather agencies are not infallible, and a tornado can occur during a tornado watch without any warning. If a watch is issued, people should watch out for changes in the sky's color, swirling clouds, or disturbances in the landscape such as clouds of dust which can indicate the presence of a tornado.