The Federal Emergency Management Agency (FEMA) will be conducting a nationwide test of the Emergency Alert System and Wireless Emergency Alerts on Wednesday, Oct. 3 around 11:20 a.m. as part of National Preparedness Month.

A test message will be sent to all cell phones within participating wireless carriers, and users cannot opt out of the test. Cell towers will broadcast the test for about 30 minutes. Compatible cell phones that are turned on within these networks will receive a test message. Some cell phones will not receive the message and phones should only receive the message once.

The message will have a header that reads “Presidential Alert” with test that states “This is a test of the National Wireless Emergency Alerts system. No action is needed.”

The messages are part of the Wireless Emergency Alerts system which is used to warn the public about critical situations. It will use the same special tone and vibration as similar messages like weather warnings and AMBER alerts.

The test also will be carried by participating TV and radio stations, cable systems and satellite providers around 11:20 a.m. More information is available at fema.gov/emergency-alert-test.