Tornado sirens are strategically placed around cities and towns. They are activated automatically when tornado warnings are issued through news broadcasts and other media. In certain areas, tornado sirens have levers that fire or police personnel pull to activate the systems when warnings are issued.
Tornado sirens emit two separate tones. An up and down tone that lasts for three minutes signifies a weather emergency. A short tone that lasts for approximately 45 seconds signifies that all is clear and the warning has passed.
When sirens are activated, it is a warning to the public that they should seek indoor shelter immediately and wait for the all clear signal. It is important for residents to watch the local news or listen to the radio for instructions and weather updates. If there is no power, it is important to listen for updates on a battery-operated radio.
Tornado sirens are typically tested on a monthly basis, depending on local policies. In certain areas, outdoor tornado warning sirens are also activated during severe thunderstorms and weather conditions that cause the winds to top 70 miles per hour; severe winds, hail and rain can cause structural damage as well as pose danger to human life.