The cities within the county own and maintain the sirens within their cities. Johnson County Emergency Management has the primary responsibility to activate the sirens throughout the county.
There are three basic criteria to activate the sirens for tornadoes:
- The National Weather Service issues a Tornado Warning for Johnson County,
- A county trained and certified weather spotter reports a tornado; or
- A tornado is reported by a local public safety official.
Johnson County has the capability of activating all of the sirens at once or by activating one or more of established siren zones. All sirens are sounded unless the threat is clearly confined to an individual zone (or zones). During a tornado warning, the sirens will be sounded for a three minute duration in ten minute intervals (three minutes on, seven minutes off) for as long as the tornado warning is in effect. There is NO “all-clear” siren.
What To Do When You Hear a Siren
If the outdoor warning system is heard at anytime other than scheduled test days, seek shelter and tune in to local radio, television, or your NOAA weather radio for instructions and information.
It is important to remember that any thunderstorm can produce a tornado with little or no warning. When a tornado warning is issued, take the following immediate safety precautions:
- In homes or small buildings: Go to a pre-designated safe area such as the basement (if available) or to an interior room on the lowest floor, such as a closet or bathroom away from windows, doors, and outside walls. Upper floors are unsafe. If there is no time to descend, go to a closet, a small room with strong walls, or an inside hallway. Put as many walls as possible between you and the outside. Get under a sturdy protection (heavy table or work bench), cover yourself with some sort of thick padding (mattress, blankets, etc.), and use your arms to cover your head and neck to protect against flying debris.
- In schools, hospitals, factories, or shopping centers: Go to interior rooms and halls on the lowest floor. Stay away from glass enclosed places or areas with wide-span roofs such as auditoriums and warehouses. Crouch down and cover your head and neck. Centrally-located stairwells are good shelter.
- In high-rise buildings: Go to interior small rooms or halls. Stay away from exterior walls or glassy areas.
- In cars: IF POSSIBLE, DRIVE AWAY! If not, get into a sturdy shelter (building). As a last resort, you need to make a personal decision whether to ride it out in your car hunched down below the windows with your SEATBELT ON, or to lie flat in the nearest ditch or depression with your hands covering your head. Be alert for flash floods. It is not recommended to seek shelter under overpasses.
- In mobile homes: ABANDON THEM IMMEDIATELY! Most deaths occur in cars and mobile homes. If you are in a mobile home, leave it and go to a sturdy building providing greater protection. If your mobile home community has a designated shelter, make it your safe place.
If no suitable structure is nearby: Lie flat in the nearest ditch or depression and use your hands to cover your head. Be alert for flash floods.
Listen to a battery-powered NOAA weather radio or local radio or television station for updated information and to determine when conditions are safe.