Outdoor Warning Sirens


Hamilton County has 75 outdoor warning sirens throughout the county.  Sirens are only intended to warn people who are outdoors and not intended to warn residents in their home.  Sirens are owned and maintained by the municipality where the siren is located.  Emergency Management maintains a memorandum of agreement with siren owners to sound the sirens during severe weather.  There are multiple nodes that send information to the sirens allowing for redundancy in the system.

emergency siren

Outdoor Sirens

There are currently 75 outdoor warning sirens in Hamilton County:
  • Town of Arcadia - 1
  • Town of Atlanta - 1
  • The City of Carmel and Clay Township - 21
  • Town of Cicero - 2
  • Indiana Academy - 1
  • The City of Fishers, including Delaware and Fall Creek Townships - 20
  • The City of Noblesville and Noblesville Township - 19
  • Town of Sheridan - 1
  • The City of Westfield and Westfield-Washington Township - 8
  • White River Campground - 1 (owned/maintained by Hamilton County)

Sounding the Sirens

Hamilton County Emergency Management sounds the sirens when the National Weather Service issues a tornado warning or when a trained weather spotter or public safety personnel sees a funnel cloud or tornado.  Sirens are grouped geographically by the municipality and sounded together when the warning criteria are met.  For example, if a tornado warning by the National Weather Service includes a portion of Noblesville, all of the Noblesville sirens will be sounded.  The only time all 75 sirens will be activated is if a tornado warning polygon includes the entire county.  

Most of the outdoor warning sirens are capable of producing multiple tones (wail, steady, and fast wail); however, only the wail tone is used for severe weather.  We do not use an all-clear sound.  To know if the all-clear is given, listen to your NOAA Weather Radio for the warning to expire or listen to NOAA Weather Radio on the free Hamilton County Emergency Management, Indiana App.

Sirens could potentially be used to alert people of a shelter in place or evacuation order; however, this would be done at the direction of the siren owner.

History and Why Sirens

Civil Defense first installed sirens as air raid sirens to warn the public of a possible attack or nuclear war.  Civil Defense eventually transitioned to Emergency Management, taking an all-hazards approach.  Sirens began being used for tornado warnings.  As communities have expanded, so have the sirens.


Hamilton County tests all sirens on Fridays at 11:00 a.m., starting the Friday before the statewide tornado drill and ending last Friday in October.   The sirens are automatically sounded, and a report is sent to siren owners.  The information is reviewed for any potential issues.  If maintenance is required, the siren own will contact their service provider to repair the siren.

The system continuously checks the sirens to ensure they are in working order.  For example, if the power goes out at a siren site, a message is sent to the system administrators stating the siren is on battery backup power.  The system checks for communications, battery status, and many other settings year-round to ensure the system is always ready for activation.

National Oceanic and Atmospheric Administration (NOAA) All-Hazards Weather Alert Radios

The best way to receive watches, warnings, and emergency messages is through an NOAA All-Hazards Weather Radio.  Weather radios are inexpensive and may include battery backup, solar charging, hand-crack power, or a USB connection to charge cell phones. Hamilton County Emergency Management recommends every household in the county have a radio as a way to receive important information even if power and the internet are out.
Weather Radio

Remember, outdoor warning sirens are intended to notify people who are outdoors that there is a severe weather situation occurring, and they should seek shelter immediately. The outdoor warning sirens are not intended to warn people indoors.