Alerts, Notifications, and Warnings

Denver's Emergency Alerting Systems

The City and County of Denver uses several tools to alert residents and visitors about emergencies as they happen and provide clear guidance on how to stay safe. Some systems require sign-up, while others are automatically enabled. Review the alert types below to ensure you’re prepared to receive timely and important information during emergencies and disasters.

Reverse Emergency Notifications (REN)

Denver’s Reverse Emergency Notifications (REN) send alerts by voice call, text message, or email when there is police activity or another safety concern in your chosen areas. These alerts include brief instructions on how to stay safe.

Residents can sign up by providing their contact details and preferred locations—such as home, school, or work—and may update or change their preferences at any time. You can also opt out of alerts by pressing “0” during a voice call or replying “STOP” to a text message.

Wireless Emergency Alerts (WEA)

Wireless Emergency Alerts are short emergency messages sent directly to mobile phones during serious public safety incidents. These alerts are used for situations such as extreme weather, evacuation orders, public safety threats, or other emergencies where immediate action may be needed.

WEA messages are sent automatically to capable mobile devices in a specific geographic area. You do not need to sign up to receive them. Alerts include brief instructions on what actions to take to stay safe. Unlike Reverse Emergency Notifications, WEA cannot be customized to specific addresses and cannot be opted into or out of beyond your phone’s emergency alert settings.

Smart911 Alerts (ADA Accommodations)

If you have a disability or need assistance during emergencies, Denver’s Smart911 system lets you create a safety profile that shares your needs with 911 dispatchers automatically when you call for help. This can include mobility needs, communication preferences, medical equipment, or emergency contacts.

Additional Information about Denver's Alerting Capabilities

Denver has has the ability to notify residents and visitors of emergencies as they happen while also providing guidance on how people can remain safe through an incident. Click the tabs to learn more about our alerting capabilities.

All-Hazard Sirens

Denver’s Outdoor Warning Siren System was installed between 2012 and 2014 and includes 86 sirens: 75 across the city and 11 at Denver International Airport (DEN). The system was originally used for tornado warnings but, as of 2023, can be activated for any major or widespread emergency—such as tornadoes, dam failure with flooding, wildfires, hazardous materials, or other urgent threats.

Sirens are designed to be heard outdoors. When a siren sounds:

Seek shelter indoors immediately and close all windows and doors.
Check your phone, computer, radio, or local media for more information and instructions.
Follow all official guidance to remain safe.

There is no “all clear” siren. If sirens continue or sound again, continue to follow protective actions.

Download the Outdoor Warning Siren Factsheet (PDF)(PDF, 38MB)

In addition to our alerting technology, we encourage members of the public to follow our social media at facebook.com/DenverOEM and X.com/DenverOEM (formerly Twitter) to receive important information, including life-safety guidance during emergencies and disasters.

Emergency Alert System (EAS Alerts)

The Emergency Alert System (EAS) is a nationwide warning tool used to deliver emergency messages through radio and television. These messages are issued by local, state, or federal officials and can interrupt scheduled programming.

EAS alerts may be shown on screen as text, with or without audio.
Programming is only interrupted once per alert, although messages may be repeated.
Messages may include translated text or audio, depending on the broadcaster.