The City and County of Denver’s Outdoor Warning Siren System was installed between 2012 and 2014. There are 86 sirens citywide: 75 in the city and 11 at Denver International Airport (DEN). The sirens are primarily used for tornado warnings, but can be used for any emergency where the public needs to seek shelter quickly. The sirens are tested on the second Wednesday of every month at 11:00 am.
What to do when the sirens sound
During a real emergency, the sirens will sound for 3 minutes at a time. Depending on how long the warning period lasts, the sirens may be resounded multiple times throughout the warning period.
When you hear Outdoor Warning Siren System, you should:
- Seek shelter indoors, preferably in a stairwell, basement, or the lowest building level. If there is no basement, go to the center of an interior room on the lowest level (closet, interior hallway) away from windows, doors, and outside walls. Put as many walls as possible between you and the outside. Do not open windows.
- Once you are inside a secure location, tune to local media (TV, radio, mobile device, etc.) or NOAA weather alert radio to be informed of the storm location, path and the duration of the warning.
- There is no “All Clear” sound that the sirens make, nor does the National Weather Service (NWS) issue an all clear message. Once the warning period has expired or is cancelled, it is safe to leave your shelter location. Be aware, however, that the NWS may extend the warning or issue a new warning at any time, so remain vigilant.
- The NWS is the only official source of severe weather warnings/watches, including tornados. All tornado warnings are initiated by the NWS. However, the City and County of Denver may sound the sirens without a NWS issued warning if a tornado has been sighted by trained observers.