Boulder County, Colo. - The Boulder County Sheriff’s Office is rolling out updates to the county’s emergency alert and warning system, including the introduction of a patrol vehicle Hi/Lo evacuation siren and new standardized terminology designed to make evacuation instructions clearer and faster to understand during life‑threatening emergencies.

These changes reflect a coordinated effort among Front Range counties participating in the Front Range Wildfire‑Initiated Community Conflagration (WICC) Initiative, a regional project focused on improving alerting, evacuation, and fire‑response capabilities.

Communities around Boulder County are joining together to roll out these updates. The Boulder County Sheriff’s Office will implement the new Hi/Lo patrol vehicle evacuation siren and updated alert terminology beginning Aug. 4. Other participating agencies including the Boulder Police Department, Erie Police Department, Lafayette Police Department, Longmont Public Safety, and Louisville Police Department, will adopt the same terminology and begin using Hi/Lo sirens on their own implementation timelines as their internal preparations are finalized.

Hi/Lo Evacuation Siren: “When You Hear Hi‑Lo, It’s Time to Go.”

The Hi/Lo siren is a distinct two‑tone alert used only when immediate evacuation is necessary. Law enforcement will activate the patrol vehicle siren while driving through impacted neighborhoods to notify residents directly, even when cell service, internet connectivity, or power are disrupted.

The Hi/Lo siren does not replace existing alert tools; it adds a reliable, on‑the‑ground method to reach people during fast‑moving emergencies such as wildfires, flash floods, hazardous materials incidents, or major law enforcement operations.

When residents hear the Hi/Lo siren:

• Evacuate immediately
• Follow instructions from responders
• Monitor official alerts
• Don’t wait for confirmation if conditions worsen

An audio example of what the Hi/Lo siren sounds like is available.

Updated Alert and Warning Terminology

To reduce confusion and align with best practices adopted across the Front Range, Boulder County is updating the language used in emergency alerts. These standardized terms will be used by multiple counties and agencies participating in the WICC Initiative.

Order to Evacuate: There is an immediate threat to life. Leave without delay. Emergency responders may not be able to assist once conditions deteriorate.

Warning to Evacuate: There is a significant threat to life or property. Residents should prepare to leave immediately. Those needing extra time, including individuals with access or functional needs, pets, livestock, or transportation limitations, should evacuate.

Shelter in Place: Conditions outside are more dangerous than remaining indoors. Go inside, secure doors and windows, and stay put until responders provide further direction.

The term “Advisory” will no longer be used due to frequent confusion with National Weather Service products.

Part of a Multi‑Layered Alert System

No single alerting tool reaches everyone. The Hi/Lo siren is one component of Boulder County’s layered system, including: Everbridge (BOCO Alert), Wireless Emergency Alerts, Emergency Alert System, outdoor warning sirens, door‑to‑door notifications, Hi/Lo vehicle sirens, and local news and official social media channels.

Boulder County residents are encouraged to sign up for Everbridge alerts at BoCoAlert.org.

Front Range WICC Initiative: A Regional Effort

The alert and terminology updates are part of the Front Range WICC Initiative, a collaborative effort involving more than 100 first responder and emergency management agencies across the Front Range. Current WICC participants include the counties of Adams, Arapahoe, Boulder, Broomfield, Clear Creek, Denver, Douglas, El Paso, Gilpin, Jefferson, Larimer, and the North Central Region All Hazards Planning Region.

Over the past year, participants have worked together to strengthen regional alerting, evacuation protocols, fire‑response strategies, and command and control during large‑scale, fast‑moving disasters.

The initiative’s Alert & Warning Working Group recommended adopting common terminology, plain‑language messaging, and cross‑jurisdictional coordination. Boulder County had already previously implemented most of the working group’s recommendations, the addition of the Hi/Lo vehicle sirens and updated alert and warning terminology are the changes taking place in Boulder County.

Current efforts include implementing additional working group recommendations, developing curriculum, providing training, conducting regional exercises, and onboarding agencies newly joining the WICC Initiative across the Front Range and mountain communities.

Stay Informed

More information about alert and warning terminology and preparedness is available at BoulderODM.gov.