Outdoor Warning Siren System

What You Should Know About the Outdoor Warning Siren System


Northbrook has an outdoor siren warning system installed throughout the community. The system consists of a series of sirens strategically located and is intended to provide warning of impending danger, but, you may only hear the sirens if you are outside. Once activated, the warning sirens will not be reactivated for the same incident. Sirens are reactivated for new, confirmed incidents.

The Village tests its outdoor siren system on the first Tuesday of each month at 10 a.m.


Warning System Activation


The system is designed to notify the community by Alert Warning and Attack Warning signals. The signals are standardized for outdoor warning devices by the Federal Emergency Management Agency (FEMA).

Alert Warning

An Alert Warning signal is a 3 to 5 minute steady siren. This signal is used during a severe weather emergency in the event of a tornado or funnel cloud sighting. The Alert Warning signal shall indicate to all persons to "immediately seek shelter, turn on your radio or television, and listen for essential emergency information." Please note, severe weather watches are reports of weather conditions in which tornadoes could occur. The warning system is not activated for severe weather watches.

Attack Warning
An Attack Warning signal is a 3 to 5 minute wavering siren. This signal means that an actual attack against the United States has been detected and that the Federal Emergency Broadcast System has been activated.

All Clear
The Village of Northbrook will not issue the all clear for any Alert or Attack signals. Please monitor commercial radio and television for further information.


Park District Lightning Alerts
The Northbrook Park District also operates an alert system at its parks and golf courses for lightning. One long, consistent siren signals lightning; short, repetitive sirens signal an "All Clear". 

Things to Remember


  • Know the different signals and know what to do. Look for the following danger signs:
      • Dark, often greenish sky
      • Large hail
      • A large, dark, low-lying cloud (particularly if rotating)
      • Loud roar, similar to a freight train.
  • If you see approaching storms or any of the danger signs, be prepared to take shelter immediately. If you are under a tornado warning, seek shelter immediately! Most injuries associated with high winds are from flying debris, so remember to protect your head.
  • Injury may result from the impact of a tornado or it may occur afterward when people walk among debris and enter damaged buildings. Because tornadoes often damage power lines, gas lines or electrical systems, there is a risk of fire, electrocution or an explosion.
  • Have a battery-operated radio available.