As you may have heard, Boulder County’s most recent emergency warning systems test was Monday evening. Boulder’s flood season stretches from April through August, and that means the emergency warning systems need to be tested regularly. Flash floods are no joke, but neither are the 30+ sirens of Boulder County’s outdoor warning system.

Following World War II most cities and towns in the United States incorporated siren alarm systems for civil defense. These were originally intended to warn civilians of impending air raids, hence the colloquial term “air raid sirens”. These systems remained in place while the threat shifted from air raids to nuclear attacks. Nowadays the civil defense sirens in most towns are reserved for natural disaster warnings. You may hear them called “tornado sirens” for that reason. In Boulder County we mostly use them to warn of flash floods.

imageThe next tests of the warning systems will occur at 10am and 7pm on the first Monday of the month throughout the flood season. The next tests will be on May 2, June 6, and August 1. However, July 4 will not have a test.

Boulder, Longmont, Lafayette, Lyons, Eldorado Springs, Jamestown, Superior, Erie, and CU Boulder Campus all have sirens equipped for civil defense. Just after the siren sounds, a voice message will play, briefly describing the reason for the alarm. The only city lacking an electronic voice message is Longmont. So if you hear a siren and want to know what’s going on, even if you aren’t a Longmont resident, visit

You can also do the following when a civil defense siren sounds:
Tune-in Boulder Municipal Cable Channel 8 (for those with cable TV in Boulder).
Tune-in to radio stations KOA 850 AM, KBCO 1190 AM or 97.3 FM.
Turn-on local television news channels (2, 4, 7, 9 or 31). Listen for a voice message if you are near a voice activated siren.
Refrain from calling 9-1-1 unless you are experiencing an emergency

It pays to have a plan when things go wrong. Boulder County has its sirens and emergency personnel, and your family ought to have an emergency plan as well. Visit for more information on how to prepare for the unexpected. Be safe Boulder.