***Check this section for CWS Alerts issued***. Generally, if no items are displayed CWS has not issued any alerts or tests. If you have any questions please refer to our FAQs Page or contact CWS at 925-655-0111.


The CWS may use sirens to alert you to a possible hazard in your area. It could be for any number of hazards and is sounded to draw your attention away from your daily activities. No matter the hazard, the best first protective action is to Shelter, Shut and Listen.

Sirens are tested on the first Wednesday of every month at 11:00am. For a siren location map click here.

You can find an example of a CWS siren sound and more information about our Alerts on our About CWS page.

You can register your mobile device through our Registration Page or by clicking the registration button available on all of our pages on the right side of the screen.

By phone: 925-655-0111

By e-mail:

By mail: 1850 Muir Road, Martinez, CA 94553

Yes, you can order CWS brochures by filling out this form.


CWS can alert residents and businesses within Contra Costa County that are impacted by, or are in danger of being impacted by an emergency.
The CWS message will include basic information about the incident and what specific protective actions (shelter in place, lockdown, evacuate, avoid the area, etc.) are necessary to protect life and health.

CWS is generally not used for traffic notifications or other non-life threatening incidents.

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