Knox County Emergency Management Agency maintains and operates multiple Outdoor Warning Sirens throughout the county. It is important that citizens never rely on these sirens as a source of warning while indoors, even if a siren is nearby and easily heard indoors. These sirens are only meant for and designed to alert people who are outdoors and away from other sources of warning methods.
When a siren is sounded, that is a signal to go indoors immediately and check with other local sources for additional information (such as TV and radio).
Outdoor Warning Sirens are mostly activated for severe weather and testing, however, sirens can be activated for other emergencies such as hazardous material releases affecting a large area.
Sirens will be activated for severe weather when at least one of the following occur:
- A Tornado Warning is issued inside Knox County
- A Trained Spotter confirms a funnel cloud or tornado
- A Public Safety official (Police, Fire, EMS, EMA) confirms a funnel cloud or tornado
- Severe thunderstorm winds are expected to be 70 mph or greater (National Weather Service “Considerable” damage tag or “Destructive” damage tag included on Severe Thunderstorm Warnings) based on Doppler radar and/or confirmed storm reports.
Knox County Outdoor Warning Sirens can be activated all at once, by zone (North, Central, South), or individually. By having this capability, sirens that are not in a threat area are not activated.
Storm Based Warnings
Severe Thunderstorm Warnings and Tornado Warnings are not issued based on whole counties. When the National Weather Service issues a Warning, the meteorologist will “draw” an area known as a polygon on their workstation for the affected areas. This polygon represents the actual Warning area. If you are inside the warning polygon, you should go to a safe location and monitor updates. If you are not in the polygon, you do not need to respond to the warning (but are encouraged to monitor and maintain awareness). Outdoor Warning Sirens will be activated based on the Storm-Based Warning polygon area. For more information on Storm-Based Warnings, click this link – NWS Storm Based Warnings
Other Warning Methods
As mentioned previously, it is crucial to never rely on sirens as a primary source of warning. Several factors may prevent sirens from activating such as power failure and electronic failure points. Other recommended warning methods include CodeRED, NOAA All-Hazards Weather Alert Radio, Wireless Emergency Alerts (WEA), Local Television, and Local Radio. It is strongly recommended to have multiple warning methods in case one should fail.
All Clear Tone
The Outdoor Warning Sirens do not give any “all clear” tones. When a siren is activated, it will sound for three (3) minutes before turning off automatically. It is important to remember that a siren turning off does NOT indicate that a threat is over.
Warning Sirens are usually tested at least once a month on Saturdays at approximately 11:30 A.M. excluding winter months.
Sirens will not be tested if sky conditions are mostly cloudy or inclement/severe weather is possible near the scheduled test time.