Outdoor Warning Sirens

Outdoor Warning SirenJohnson County has 33 outdoor warning sirens placed strategically throughout Lenexa as early warning devices to alert you of potential severe weather. These sirens, in conjunction with NOAA weather radios, the Emergency Alert System and local media, will help notify you during emergencies.  

Our outdoor warning sirens are not intended to warn residents who are indoors or in noisy areas.  


Typically, Johnson County tests the sirens at 11 a.m. on the first Wednesday of each month February through November. Then, at 11:15 a.m., we test the sirens from city equipment. Tests are not conducted in December or January because the extreme cold or heavy icing could damage the equipment. Tests are also canceled when severe weather or the risk of severe weather is present.  


We own and maintain our own sirens, but Johnson County Emergency Management and The U.S. Department of Homeland Security have the primary responsibility to activate the sirens for tornado warnings (steady tone) or an attack (wavering tone). We are also capable of activating the sirens, if needed.  

Sirens are activated in the following situations:  

  • The National Weather Service issues a tornado warning for Johnson County.  

  • A trained and certified weather spotter reports a tornado.  

  • Local public safety officials reports a tornado. 

When they are activated, sirens are initially sounded for three minutes, then intermittently throughout the warning period, as needed. There is no all-clear siren.  

What to do if the alarm sounds

If you hear an outdoor warning siren any time other than during a scheduled test, seek shelter immediately and tune in to your local radio, television or weather radio for more information.  

Seek shelter in the following locations:  

  • In your home: Go to a basement or an interior room on the lowest floor away from windows, doors and outside walls.  

  • In schools, hospitals, factories or shopping centers: Go to interior rooms on the lowest floor. Avoid areas enclosed by glass and areas with wide-span roofs, such as auditoriums or gyms. Centrally located stairwells are good shelter areas. 

  • In high-rise buildings: Go to interior small rooms or halls. Avoid exterior walls and areas with glass. 

  • In cars or mobile homes: Leave and go to the nearest permanent structure or tornado shelter. If no structure is nearby, lie flat in the nearest ditch and cover your head with your hands.