Outdoor Warning Siren System
The City of Naperville's siren system is comprised of 19 siren units. The sirens are tested the first Tuesday of each month at 10 a.m. The test consists of one minute of a steady tone, one minute of silence, one minute of a wavering tone, two minutes of silence and then a 10 second steady tone.
If you hear the outdoor warning sirens, do not call the Fire Department, Police Department or Office of Emergency Management. During severe weather, seek shelter immediately, and at all other times tune into 1610 AM radio, 89.1 FM radio or cable TV for information on the emergency.
What do the tones mean?
The steady tone is used to alert the public that a tornado has been sighted and is approaching the community. This tone will last three to five minutes. When the steady tone is heard during severe weather, you should seek a place of shelter immediately.
If the steady tone is heard at any time other than during severe weather, it is a signal that an emergency is occurring in the community and you should tune to local Cable TV, 89.1 FM or 1610 AM radio for information.
The wavering tone is used only as a "take cover" signal of imminent danger of an nuclear attack on this country.