Outdoor Warning Sirens

Outdoor Siren System Siren image

Hamilton County's Outdoor Warning Siren System consists of approximately 190 strategically-placed sirens. These sirens serve as an early warning device to alert citizens to take shelter indoors and seek additional information. While the outdoor warning system can be an effective method of notifying those that are outdoors, to seek shelter indoors, it is only one component of a comprehensive emergency warning system. In addition, you should sign up for Alert Hamilton County (www.alerthc.org) to receive phone calls, text messages and/or emails about hazards that may impact your safety. This is in addition to our recommendation that you obtain a NOAA weather radio and tune in to local media reports from television, radio, or social media. We encourage you to have multiple ways to receive emergency notifications.

Designed as an Outdoor Warning System, the sirens SHOULD NOT be relied upon to provide sufficient warning INDOORS or in NOISY AREAS. Additionally, air conditioning, thunder, wind, rain, and other conditions can cause the sirens not to be heard indoors or outdoors, even if sirens can be heard during monthly tests. Sirens are also subject to lightning strikes and other equipment malfunction. Because the sirens are constantly exposed to the elements and other hazards, Hamilton County EMHSA cannot guarantee that the sirens will function correctly. For these reasons, everyone is encouraged to have multiple ways to receive information about severe weather.

For additional information regarding Hamilton County's Outdoor Warning Siren System, refer to the following informational sheets, which are available in Arabic, English, Spanish, French and Nepali:

Activation Criteria

There are three basic criteria that Hamilton County EMHSA uses to activate the sirens:

  1. The National Weather Service (NWS) issues a Tornado Warning for Hamilton County.
  2. A tornado is reported by a local public safety official (police/firefighter) to the NWS or to Hamilton County EMHSA.
  3. A dangerous situation occurs which requires the public to seek shelter indoors immediately.

Hamilton County has the capability of activating all of the sirens at once or by activating one or more of six 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.

Siren Test Cancellation Criteria

Basic criteria for cancelling the activation of the Outdoor Warning Sirens include:

  1. Extreme cold, freezing rain/drizzle, and/or icing that may damage the equipment.
  2. Presence of severe weather (or potential severe weather) occurring in the local area, which may cause confusion as to whether the activation is a real event.

Monthly Testing

The Outdoor Warning Siren System will be tested on the first Wednesday of each month at 12:00 p.m., unless there is inclement weather in Hamilton County. A siren test will consist of a single siren tone, lasting approximately 1 minute. Hamilton County EMHSA will notify the public via press release and social media posts when a siren test is planned, cancelled, or rescheduled, prior to the time at which the sirens will sound.

If Hamilton County is experiencing severe weather prior to 12:00 p.m. on a scheduled test day, the siren test may be postponed, to the determined alternate test day, which is the second Wednesday of the month, at 12 p.m. Testing for the alternate day will consist of a "Growl" test. A "growl" test is a quick sounding of the sirens, lasting approximately six seconds, which tests the activation and rotation of each siren. If testing the sirens on the alternate day is also canceled, the Outdoor Warning Siren tests will resume on the next scheduled monthly date.

Siren testing may be suspended during the winter months (December – February) when ice or sub-freezing temperatures could damage the siren system. If there is an emergency during winter months, the sirens will be activated to notify people of the need to seek shelter.

If testing is required at any time outside of the normal monthly testing schedule, Hamilton County Emergency Management and Homeland Security Agency will be sure to notify the public via social media posts and press release.

Siren Maintenance

Hamilton County EMHSA maintains approximately 190 sirens throughout the county. Each siren is inspected at least every three years. The maintenance/inspection program as adopted by Hamilton County EMHSA consists of checking the operations of the siren, battery strength, terminal connections, site conditions, and obstructions that may interfere with the siren. During maintenance and inspection, the siren is "growled." This short activation may occur several times during our inspection. If you have questions regarding a siren being sounded in your neighborhood, please feel free to contact Hamilton County EMHSA. The agency has partnered with Hamilton County Facilities to perform maintenance on the sirens. Hamilton County employees always carry appropriate identification and have appropriate signage displayed when servicing sirens.

Why is the Outdoor Warning Siren System activated?

Under the Hamilton County Outdoor Warning Siren System guidelines, sirens will be sounded when:

  • The National Weather Service (NWS) issues a Tornado Warning for Hamilton County.
  • A tornado is reported by a local public safety official (police/firefighter) to the NWS or to Hamilton County EMHSA.
  • A dangerous situation occurs which requires the public to seek shelter indoors immediately.

When are the sirens tested?

Sirens will be tested on the first Wednesday of each month at 12 p.m. During a test, the sirens will sound for approximately one minute.

Who activates the sirens?

Sirens are activated by Hamilton County Emergency Management and Homeland Security Agency or the Hamilton County Communication Center.

Why are siren tests cancelled?

If Hamilton County is experiencing severe weather on the day of a test, the test will be postponed until the second Wednesday of the month. A "growl" test will be conducted on the alternate day. A "growl" test activates the system without a full audible alert of the system. A growl lasts approximately six seconds.

To reduce the potential impact of damage, the sirens may not be tested during the months of December through February, due to prolonged periods of extreme cold temperatures or ice and snow accumulation. However, if there is an emergency during winter months, the sirens will be activated to notify the public to seek shelter.

What should I do when I hear the sirens?

Immediately seek shelter indoors. If possible, go to the lowest level, and shelter within the most-interior room of the structure, avoiding all windows. Tune in to a NOAA All-Hazards Radio and/or local media for more detailed information about the situation. Remember: Take cover, tune in, take action!

How long will the sirens sound during a Tornado Warning?

During a tornado warning, the Outdoor Warning Sirens will sound for three minutes. (This is different than the monthly test that sounds for approximately one minute.) After three minutes of sound, there will be a seven minute span of quiet. This cycling of three minutes of sound with a seven-minute silent pause in between, will last until the Tornado Warning has expired or the tornado warning is canceled by the National Weather Service.

Do the Outdoor Warning Sirens sound an all-clear signal?

There will be no "all clear" signal from outdoor warning sirens. During severe weather, tune in to local media and trusted media sites for updates.

Can I hear the sirens indoors?

Sirens are not guaranteed to be heard indoors. Sirens are part of the Outdoor Warning Siren System, designed specifically to alert those outside to seek immediate shelter indoors.

Why do I hear the outdoor warning sirens during a thunderstorm or rain?

The Outdoor Warning Sirens in Hamilton County will only sound during a Tornado Warning or to indicate the need to seek immediate shelter indoors. The sound you may be hearing could be from electronic lightning detection alert systems on local golf courses. These systems sound a small siren for a short period of time (approximately 15 seconds) if lightning is detected nearby.

Where can I read the Outdoor Warning Siren System guidelines?

See above for the Outdoor Warning Siren System Guidelines.

Why were the Outdoor Warning Siren guidelines developed?

By adopting common outdoor warning system guidelines, confusion can be minimized and response time reduced.

How can I get weather alerts when I am at work or at home?

Signing up for Alert Hamilton County (www.alerthc.org) is a great way to get weather or other hazardous situation alerts in Hamilton County. These alerts are specific to your home and/or work address. You can include as many addresses in your profile as you wish, so that you will be notified while at work, home, or school! We also encourage residents and businesses to get a NOAA All-Hazards Radio in order to receive up to date weather information and alerts.

How can I stay safe during a storm?

Storms have the potential to produce dangerous lightening or high winds. When you get a weather alert or warning, take immediate shelter indoors, tune in to local media for updates and information, and take the appropriate action.

Who do I contact if a siren in my neighborhood is not working?

If your neighborhood siren is not functioning properly, you should contact the Hamilton County Emergency Management and Homeland Security Agency, at (513) 263-8200. Please provide the siren location and a description of the problem.