The Trump administration plans to send out a message to all cellphones in the U.S. Thursday, a test of an alert system for national emergencies. The test is scheduled for 2:18pm ET and will come across as "Presidential Alert."
The message will indicate it is just a test. The Federal Emergency Management Agency was required to create the alert system under a 2016 law requiring the President to be able to send out nationwide messages. It's similar to other regional emergency messages about weather events or missing children.
Source: Time