https://www.fcc.gov/consumers/guides/emergency-alert-system-eas
If you don't have a smartphone, but can receive test messages on your computer (e.g. Google Voice) -
How do I get emergency text alerts?
Sign Up for Alerts
Subscribe to alerts for your neighborhood, schools, businesses, media, and other interest areas. Powered by Everbridge. Nixle – Text your zip code to 888777 to opt-in or sign up online to receive email, text or voice messages with alerts and advisories from local law enforcement.