The federal government will test its nationwide emergency alert system today at 11:20 a.m. in Arizona and 12:20 p.m. on the Navajo Nation.
Mobile customers whose phones are on will hear an alert, their phones will vibrate and then a message will flash across their screens about the test.
People watching television or listening to the radio will also see or hear the message.
There is no way to opt out of the test.
These types of alerts are frequently used in targeted areas to alert people to things like natural disasters, acts of terrorism or other public safety threats.
The test is being done across the country.
Federal law requires the systems to be tested at least once every three years and the last one was in 2021.