The alert, scheduled for 7.18pm BST (2.18pm ET) will be the first trial of the system, which is part a new collaboration with The Federal Emergency Management Agency (FEMA).
Cellphone users across the United States will receive a "President Alert" at 1:18 p.m.
That sprouted from a 2006 Congressional act passed to fund a national alert system that President George W. Bush called for after the federal government's bungled Hurricane Katrina response in 2005, according to CNET.
Alerts like the one shown here are set to pop up on cell phones Wednesday afternoon during a nationwide alert system test. Users can not opt out of receiving the WEA test. The EAS, familiar to those who have grown up in the USA, is used to broadcast national emergency alerts over television, radio, cable, satellite radio and other pre-internet mass media channels.
Unfortunately, you can not easily opt out of the Presidential Alert, but there are a few workarounds that might work, although they're hard to implement.
If you still believe you were near a tower and didn't get the alert or if you want to provide feedback, FEMA wants to hear from you. "But people don't get their messages the way they used to".
Our President now has another way to reach you.
FEMA reported that people wouldn't be able to turn off this presidential alert.
The WEA test message will read "THIS IS A TEST of the National Wireless Emergency Alert System". This is the first national WEA test. This system was developed by broadcast and cable operators in voluntary cooperation with the Federal Emergency Management Agency, the Federal Communications Commission, and local authorities to keep you informed in the event of an emergency.
FEMA officials said Tuesday they would share test result data on how the testing went with mobile carriers to help ensure the system works well in a true emergency. Your phone might have alerted you that the test message arrived in a slightly different manner than normal text notifications.