If you hear the sound of a blaring siren in your neighborhood, take note: That’s what it will sound like if a tornado is headed your way.

In parts of Colorado this morning, including Denver, safety officials will test those screaming air-raid-style sirens voluntarily between 9 a.m. and 11 a.m. (via 9News). Denver has 76 sirens, including nine at Denver International Airport, that are scheduled to blare at 9:15 a.m.

The city of Aurora, which has added a new siren outside the Southlands Mall after a tornado struck last June, won’t be testing its roughly 60 sirens until next month.

Additionally, the National Weather Service drill will include interruptions on broadcast television stations with practice warning messages to determine the readiness of emergency communications equipment and emergency radio receivers in broadcast facilities, schools, hospitals, and other public buildings, writes Fox 31. Remember: This is only a test.