High Quality Content by WIKIPEDIA articles! A tornado warning (SAME code: TOR) is an alert issued by government weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation. When this happens, the tornado sirens may sound in that area, letting people know that a tornado was seen or is forming nearby. Issuance of a tornado warning indicates that residents should take immediate safety precautions. It is a higher level of alert than a tornado watch, but it can be surpassed by an even higher alert known as a tornado emergency.