The Outdoor Warning Sirens will be tested audibly on the first Wednesday of each month at noon if weather conditions are favorable.
These sirens are designed to alert citizens, who are outdoors, to an imminent threat in the community. When sounded, citizens should seek shelter immediately in a stable structure. Once secure, citizens should listen to a radio and/or television for emergency warning details and further instructions.
Tornado Sirens
While tornado warnings are the most common cause for siren activation, the sirens should not be considered to be "tornado sirens." They are intended as an "all-hazards" alerting system and may be activated for any type of emergency situation. The sounding of the sirens does not necessarily mean that a tornado warning has been issued. In fact, it means only that an emergency event has occurred or is about to occur and you may need to take action to protect yourself.
Signal
If you hear a siren, you should immediately seek additional information through local radio and television stations. In all cases, the siren warning signal is a three-minute steady blast with each siren lighting a ring of red LED lights while the sirens are active.
Activated Siren Reasons
Sirens will be activated for:
- Chemical spill emergency
- Other emergencies as appropriate
- Reports or suspected hail larger than 1.75 inches
- State or national emergency declared by the governor or president
- Sustained winds in excess of 70 miles per hour
- Tornado or funnel cloud reported by a reliable source
- A tornado warning issued by the National Weather Service When sirens sound, seek shelter and seek information
Hearing the Sirens
The most important thing to know about these sirens is that they are designed to alert individuals who are outdoors. Sirens are not intended to alert people who are in cars, homes, or other buildings. Hearing sirens indoors may have been possible in the past; however, this should no longer be expected.
Indoors
Energy conservation practices and better insulation have effectively reduced the sound penetration into these areas. In addition, many homes and businesses are air-conditioned. Very few buildings have open windows in the summer when it is hot and humid - the very time when severe weather is most likely to occur.
The Range of the Siren
A number of factors affect the range of the siren - sound output, atmospheric conditions, topography, and ambient noise levels. Very simply, some sirens are designed to be louder than others. A louder siren will have a greater range. Atmospheric conditions, such as wind speed and direction, air stability, and relative humidity, all affect the distance that the sound will travel.
Changing Conditions
Your ability to hear the siren will change as these conditions change. It is very possible that from your location, in some cases you will be able to hear the siren, while in other cases, you won't. Topography and background noise levels will also have an effect on your ability to hear the sirens.
Hills, trees, and buildings can be barriers that block the sound. High background noise levels from highways or industrial areas can mask the sound of the siren. These conditions will effectively limit the warning range of the siren.
Disruptions
Sirens can also be very susceptible to disruptions in the electrical power supply. A majority of the sirens operate on power supplied by local utilities. Power failures, which are common during thunderstorms, can disable a siren. In addition, lightning striking a nearby power line can blow fuses in the siren itself. This will also disable the unit until the fuses can be replaced.