This Thursday the President will send out an Emergency Alert Test to your phone. Most cell phone users will receive the test at 2:18 PM Eastern time.
This emergency test it is part of the Federal Emergency Managment Agency System to warn us in case of a national emergency.

We already receive these tests via Radio and T.V, they will be similar to the Ambert Alert received on your phone and you can also opt out from receiving the alerts.

FEMA, however, said it could postpone the test to October 3rd if the agency is dealing with other natural disasters.

There will be more than 100 carriers participating including Verizon, AT&T, Sprint, and T-Mobile.