MEMPHIS, Tenn. — If you live in Shelby County, you’ve heard a siren that goes off every Wednesday for years now, but what does it mean?

Shelby County, the city of Memphis, and Millington conduct warning siren testing on Wednesdays at 3:30 p.m. every week.

Even though it is possible to hear indoors, the sirens were specifically made for those outdoors as a pre-incident warning when a storm approaches.

The siren tests are conducted by the City of Memphis Office of Emergency Management.

Although they are referred to as tornado sirens, Tennessee 211 says the warning devices may also go off to warn a large population about an impending disaster, hence why it needs to be tested weekly.

Collierville, Bartlett and Germantown conduct siren testing each Saturday at noon.

To learn more, visit MemphisWeather.net.