This week the Federal Emergency Management Agency (FEMA) will do its first test of a system that allows the president to send a message to most U.S. cellphones.

"The EAS [Emergency Alert System] is a national public warning system that provides the President with the communications capability to address the nation during a national emergency," FEMA said on its website.

The WEA portion of the test commences at 2:18 p.m. EDT on Thursday, September 20, and the EAS portion follows at 2:20 p.m. EDT. The test will assess the operational readiness of the infrastructure for distribution of a national message and determine whether improvements are needed.

The WEA test message will be sent to cell phones that are connected to wireless providers participating in WEA. This is the fourth EAS nationwide test and the first national WEA test. Previous EAS national tests were conducted in November 2011, September 2016,  and September 2017 in collaboration with the FCC, broadcasters, and emergency management officials in recognition of FEMA’s National Preparedness Month.

The EAS is a national public warning system that provides the President with the communications capability to address the nation during a national emergency. The test is made available to EAS participants (i.e., radio and television broadcasters, cable systems, satellite radio and television providers, and wireline video providers) and is scheduled to last approximately one minute. The test message will be similar to regular monthly EAS test messages with which the public is familiar. The EAS message will include a reference to the WEA test:

“THIS IS A TEST of the National Emergency Alert System. 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. If this had been an actual emergency an official message would have followed the tone alert you heard at the start of this message. A similar wireless emergency alert test message has been sent to all cell phones nationwide. Some cell phones will receive the message; others will not. No action is required.”

Cell towers will broadcast the WEA test for approximately 30 minutes beginning at 2:18 p.m. EDT. During this time, WEA compatible cell phones that are switched on, within range of an active cell tower, and whose wireless provider participates in WEA should be capable of receiving the test message. Some cell phones will not receive the test message, and cell phones should only receive the message once. The WEA test message will have a header that reads "Presidential Alert" and text that says:  “THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed.”

The WEA system is used to warn the public about dangerous weather, missing children, and other critical situations through alerts on cell phones. The national test will use the same special tone and vibration as with all WEA messages (i.e. Tornado Warning, AMBER Alert). Users cannot opt out of the WEA test.