When is the big emergency alert test? Expect your phone to ominously blare today.

On Wednesday at 2:20 p.m. Eastern, 1:20 p.m. Central, 12:20 p.m. Mountain and 11:20 a.m. Pacific time, every TV, radio and cellphone in the United States should blare out the distinctive, jarring electronic warning tone of an emergency alert.

No need to worry. It's simply the Nationwide Emergency Alert Test. The massive national trial, the first since 2018, is scheduled to last approximately one minute.

It will only go out once, there will be no repeats.

It's a way for federal emergency management coordinators to make sure the national alert system is still an effective way to warn Americans about emergencies, natural catastrophes, attacks and accidents at the national level.

What will the emergency alert test message say?

All across the United States, broadcast TV shows and radio will be interrupted as the emergency message goes out. That message will say:

“This is a nationwide test of the Emergency Alert System, issued by the Federal Emergency Management Agency, covering the United States from 14:20 to 14:50 hours ET. This is only a test. No action is required by the public."

Cellphones will get the warning as a tone, a vibration and as a text message:

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

Phones in which the menu is set to Spanish will see this: “ESTA ES UNA PRUEBA del Sistema Nacional de Alerta de Emergencia. No se necesita acción.”

At what time will the emergency alert test happen?

The alert will air at the same moment across every time zone in the country starting at 2:20 p.m. EDT on Wednesday, Oct. 4. The time will vary across time zones, so look to see when you might be alerted:

  • 2:20 p.m. EDT

  • 1:20 p.m. CDT

  • 12:20 p.m. MDT

  • 11:20 a.m. PDT

  • 10:20 a.m. ADT

  • 8:20 a.m. HST

Will you get the message if your phone is turned off?

Only cellphones that are turned on will receive the message. If your phone is on but the sound and vibration features are turned off, you'll still get the message.

If your phone is set to Wi-Fi or airplane mode, it won't receive the alert because the message goes out over the cellular broadcast system.

How loud will the alert be?

The type of noise and general volume of the alert is similar to that of an Amber Alert or warnings issued by the National Weather Service in case of severe weather.

READ MORE: Massive emergency alert test scheduled to hit your phone on Wednesday. Here's what to know.

This article originally appeared on USA TODAY: US emergency alert test Wednesday: What time will the big test happen?