On October 3rd, FEMA will conduct a test of its Integrated Public Alert and Warning System (IPAWS), which brings together two existing alert systems, the Emergency Alert System and the Wireless Emergency Alerts system. This system will also mark the first time that a “Presidential Alert” will be sent out to a majority of cell phone owners, who won’t be able to opt out.

The test was originally scheduled for September 20th, but has been postponed to the backup date due to ongoing severe weather conditions and accompanying response efforts in some regions of the United States. It will take place at 2:18 PM.

TechCrunch notes that these types of alerts were established in 2006 under President George W. Bush, so that the White House can issue a notification to the general public in the instance of an emergency. The messages can be sent at the President’s discretion, but while experts have downplayed the possibility of the system being misused, this is the first time that the message will come with the heading “Presidential Alert.” FEMA also notes that users also won’t be able to opt out of receiving the text messages.

The agency says that it’s testing the system to “assess the readiness” for a national emergency message, and to “determine whether improvements are needed.” The WEA test will take place at 2:18PM ET on the 20th in the form of a text message to cell phones (which will come with a different ringtone and vibration), while the EAS test will take place two minutes later via television, radio and wireline providers, with more than 100 providers participating in the test. Any cell phone that is “switched on, within range of an active cell tower, and whose wireless provider participates in WEA should be capable of receiving the test message.”

FEMA released the text of the message, and notes that it’s the fourth test of the EAS system (it was tested in November 2011, September 2016, and September 2017), but that this is the first time that the WEA system has been tested nationwide.

“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 toall cell phones nationwide. Some cell phones will receive the message; others will not. No action is required.”

The WEA system is the same one that’s used to alert the public in the event of an AMBER Alert or a critical weather situation, and it comes after a terrifying incident in January when an alert went out in January that warned Hawaii residents that a missile was about to strike the state. Following that false alarm, the FCC launched an investigation, and it became clear that the test went out by mistake because of human error and a poorly designed computer interface. The FCC also noted that it will make some additional changes to the system.

Updated September 17th, 2:00PM ET: This article has been updated to reflect the postponed date of the FEMA test alert message.