President Donald Trump talks to reporters on the South Lawn of the White House in Washington, October 2, 2018.

There's a good chance that Wednesday afternoon, around 2:18 p.m. ET, your phone will sound an alarm and receive a message that says "Presidential Alert."

Don't worry about it.

This is a joint test by FEMA and the FCC of the existing emergency alert system (EAS) and wireless emergency alerts (WEA).

You're probably already aware of WEA messages. They warn you about severe weather, such as flooding, in your area. Or you might have received a WEA AMBER alert if a child is missing.

Wednesday's message will simply read: "THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed."

It isn't coming from President Donald Trump, but in the future it might if there's a national emergency.

It will sound just like the alerts you get for severe weather, with a sort of piercing loud noise. Also, FEMA says you can't opt out of it, so prepare for it Wednesday afternoon. The test will last for about a half hour.

Another test, through EAS, will send a similar message to TV, radio, cable and satellite providers. This alert will last about a minute, FEMA said.

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