On Wednesday, October 4 in the U.S., the Federal Emergency Management Agency (FEMA) will test its Wireless Emergency Alerts (WEA) system

At 2:20 p.m. Eastern, people will receive a message on their mobile phones that reads

“THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed.”

In addition to the message, your iPhone will vibrate and play “a special sound that’s similar to an alarm” even if your iPhone is on silent.

The alert will appear in Spanish for users who set their devices for that language. 

FEMA is conducting the test to check for effectiveness in need of emergencies.