On May 4, many of our readers heard a tornado siren, a sign that a twister could be nearby.

The city of Decatur says, “The the siren system was designed to alert residents and visitors who are outside that a tornado may be imminent. The system was not designed to be heard within a home or building though if you live or work near one, you will likely hear a siren while indoors.”

The city said in a press release that it sounds the alarm when the National Weather Service issues a tornado warning in the Decatur area or if a member of the city’s public safety staff spots a tornado. The sirens go off for three to five minutes per warning.

So what should you do if you hear a siren? The city says if you are ….

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– In a building – go to a pre-designated shelter area. Stay away from corners, windows, doors and outside walls. Put as many walls as possible between you and the outside. Get under a sturdy table and use your arms to protect your head and neck. Do not open windows.

– In a vehicle, trailer or mobile home – get out immediately and go to the lowest floor of a nearby, sturdy building or storm shelter. Never try to outrun a tornado in an urban or congested area in your vehicle.

– Outside with no shelter – lie flat in a nearby ditch or depression and cover your head with your hands. Be aware of the potential for flooding. Do not get under an overpass or a bridge. You are safer in a low, flat location. Watch out for flying debris, which is the cause of most fatalities and injuries during tornadoes.

Even if residents do not hear a siren, they are likely to be alerted through their cell phone or an alert broadcast on television.

The city of Decatur says, “Residents and business owners can sign up for Smart911 severe weather notifications for events such tornadoes, severe thunderstorms and flash flooding warnings at smart911.com. (If you already have a registered safety profile, just sign in and select or update the notifications you would like to receive.) The alerts notify residents in the areas immediately affected and are triggered by NWS polygon technology.”