Don’t be worried if your cellphone starts to buzz loudly on Thursday morning.

It is only a test.

The District’s Homeland Security and Emergency Management agency, along with about 20 other area jurisdictions, is doing a test message at the same time on Thursday between 10 a.m. and 11 a.m. for the “wireless emergency alert (WEA) system.”

This system is a way to alert residents in certain areas of safety situations. The District’s homeland security officials said the WEA system “allows the messaging to be more targeted and efficient which is critical during an emergency.”

Officials said they need to periodically test the emergency alert systems to “identify any needed improvements.” Plus, authorities said they must make sure there are “reliable methods and systems” to get out urgent messages and warnings to the public in the event of an emergency.

The text message test will read: “A test of the District of Columbia Wireless Emergency Alerts System. No action required.”

Area residents will also hear a loud noise as the text message is displayed on their mobile devices. Also participating: Alexandria, Bowie, College Park, Fairfax, Falls Church, Gaithersburg, Greenbelt, Takoma Park, Manassas, Manassas Park; Rockville; Arlington, Charles, Fairfax, Frederick, Loudoun, Montgomery, Prince George’s and Prince William counties.

Customers do not need to sign up to get the WEA alert.