A tornado warning (SAME code: TOR) is an alert issued by 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 the public, storm chasers, emergency management or law enforcement, or more commonly if there are radar indications of tornado formation. When this happens, the tornado sirens may sound in that area if any sirens are present, informing people that a tornado has been sighted or is forming nearby. The issuance of a tornado warning indicates that residents should take immediate safety precautions.