From the Apple Support website:
Learn how to turn on emergency, government, and public safety alerts on your iPhone and Apple Watch.
You can receive emergency, government, and public safety alerts on your iPhone and Apple Watch. In the event of an emergency, here’s what you might see:
- Alerts issued by your country or region’s government
- Alerts involving imminent threats to safety or life
- Alerts for extreme weather conditions
- AMBER alerts (America’s Missing: Broadcast Emergency Response)*
- Public Safety Alerts*
*AMBER alerts and Public Safety Alerts aren’t available in all countries or regions.
Turn Government Alerts on or off
By default, Government Alerts are turned on for your device.* When you receive a government alert, you hear a special sound that’s similar to an alarm. If you want to turn these alerts on or off, follow these steps:
- Go to Settings > Notifications.
- Scroll to the very bottom of the screen.
- Under Government Alerts, turn the type of alert on or off.*
*Government Alerts are supported when using a SIM card from a supported carrier. Your Apple Watch can receive these alerts if your iPhone can receive them and is nearby, or your Apple Watch is on a Wi-Fi network. With a cellular plan from a supported carrier, your Apple Watch Series 3 (GPS + cellular) can receive these alerts without your iPhone nearby. For more information, contact your carrier.
*In some countries, you may not be able to disable Government Alerts.
Choose to receive Test Emergency Alerts in the United States
When your iPhone is connected to a carrier in the United States — using a U.S. SIM or while roaming in the U.S. — you can enable Test Emergency Alerts. By default, this is turned off. When you receive this type of alert, you’ll hear a sound that’s similar to an alarm, and the alert will mention that it’s a test. To turn these alerts on or off, follow these steps:
- Open the Phone app and tap Keypad.
- To turn it on: Enter *5005*25371# and tap . You’ll get an alert that says “Test alerts enabled.”
- To turn it off: Enter *5005*25370# and tap . You’ll get an alert that says “Test alerts disabled.”
Government test alerts are available with U.S. carriers, including Puerto Rico. Your local government is responsible for the content and the frequency of the test alerts. You can disable this feature anytime with the steps above. For more information, contact your carrier.