What Is Hi-Lo?

Hi-Lo is a sound you may hear when you must evacuate immediately. This warning system is different from the sirens you hear regularly when deputies, paramedics, and firefighters respond to emergency calls.

Hi-Lo is a very distinct tone that alternates between a fixed high and low frequency sound. It quickly alerts neighborhoods that they may be in immediate danger.

Use of Hi-Lo

The San Diego County Sheriff’s Office only uses the Hi-Lo during natural disasters, extreme emergencies, or critical incidents that require the evacuation of a specific area.

Hi-Lo Emergency Notification

Hear the Hi-Lo

When you hear the Hi-Lo, it is time to go. If you are in an evacuation area, leave immediately and follow directions from law enforcement or emergency personnel.

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When Hi-Lo May Be Used

The Hi-Lo may be used during incidents that require people in a specific area to leave quickly for their safety.

Wildfires

Earthquakes

Flash Floods

Tsunamis

Sinkholes

Bomb Threats

SWAT Standoffs

Terrorism

Hazmat Incidents

Gas Leaks

What To Do If You Hear the Hi-Lo

Leave the area immediately if instructed to evacuate.
Follow directions from deputies, firefighters, and other emergency personnel.
Pay attention to official emergency alerts and updates.
Do not delay if your neighborhood is in danger.

Aerial view of a flooded neighborhood with emergency vehicles and people gathered along a partially submerged road.

Alt text: A wildfire burns along a hillside at night with bright flames and heavy smoke near an emergency vehicle with flashing lights.

A helicopter hovers above a wildfire, releasing water onto the flames and smoke below.

Why the Hi-Lo Matters

The Hi-Lo is designed to quickly alert people in a neighborhood that there may be an immediate threat. Because it is different from the sirens used by emergency vehicles responding to calls, it helps signal that the public may need to take action right away.