VIDEO: Sirens across the state sounded Thursday during Wisconsin's annual tornado drill that marks the start of the severe weather season. Sirens are strategically placed all across the state to warn people if a tornado is coming. But now that most people have smartphones and weather radios, are the sirens necessary? At Edgerton Elementary in Greenfield, principal Christopher D'Acquisto made the announcement: "The National Weather Service has issued a tornado warning. Please move quickly and quietly to your designated areas at this time."