Part of the Federal Emergency Management Agency’s Integrated Public Alert and Warning System (IPAWS), Wireless Emergency Alerts (WEA) is a public safety system that allows all who own certain wireless phones and other compatible mobile devices to receive geographically-targeted, text-like messages alerting them of serious imminent threats to safety or missing persons in their area. These emergency messages are sent by authorized government officials including local and state public safety agencies like San Mateo County DEM, the Federal Emergency Management Agency (FEMA), California Governor’s Office of Emergency Services (CalOES), Department of Homeland Security (DHS), and the National Weather Service (NWS). WEAs can be issued for three alert categories: imminent threat, AMBER (an abduction alert system), and Presidential. WEAs are only issued for the most serious emergency situations and may be targeted to focus the alert or warning on a specific geographical area that is most likely impacted by the emergency. 

Opting in or out for Wireless Emergency Alerts (WEA)  

You can opt-in or out of receiving WEA messages for imminent threat and AMBER alerts by adjusting settings on your mobile device. 
1. From the Home screen, tap Settings. 
2. Tap Notifications. 
3. From the Government Alerts section, drag the AMBER Alerts switch left or right to enable or disable. 
4. From the Government Alerts section, drag the Public Safety Alerts switch left or right to enable or disable. 

Android Phones: 
1. Open your Settings app. 
2. Tap “More” under the Wireless & Networks heading. 
3. Under the Wireless & Networks heading, scroll to the bottom, then tap Cell broadcasts. 
4. Here, you’ll see various options you can toggle on and off, such as an option to “Display alerts for extreme threats to life and property,” another one for AMBER alerts, and so on. Toggle these settings on and off.  

Not everyone will receive WEAs – here are a few reasons why: 
The system isn’t fool-proof. There are a few reasons why you may not receive an emergency alert on your cell phone, including: 
• your phone wasn't near a cell tower 
• your phone wasn't turned on 
• your phone was in airplane mode 
• older phones may not be Wireless Emergency Alert capable 
• your software needs updating (iPhones need iOS 6 or newer to receive an emergency alert) 

Presidential Alerts

An alert from the U.S. President was sent to millions of cell phones Oct. 3, 2018, as a part of a test of FEMA's Wireless Emergency Alert (WEA) system. Though FEMA and the FCC had previously tested the Presidential Alert system in several cities and states, the 2018 test was the first time a nationwide emergency alert was sent via text message. The entire point of the 2018 test was to identify problems with the system so that the FCC, FEMA, and participating cell carriers could work out any system bugs and improve the warning delivery. 
Unlike AMBER alerts, the Presidential Alert can't be turned off. You can’t opt-out of the Presidential Alert—it goes to virtually every cell phone in the country.