Hawaii’s emergency sirens use two tones. A steady, one-minute tone is the all-hazard Attention Alert Signal, used for threats like tsunamis, hurricanes, flooding, volcanic eruptions, dam breaches, wildfires, and hazardous material incidents. A wavering, rising-and-falling tone is the Attack Warning Signal, historically reserved for an imminent or ongoing attack on the United States.1Hawai’i Emergency Management Agency. All-Hazard Statewide Outdoor Warning Siren System Neither tone tells you what the threat actually is. The moment you hear one outside of a scheduled test, turn to local radio, local television, or your phone for the specific instructions that follow.
The Two Tones
Steady Tone: Attention Alert Signal
This is the tone you are most likely to hear. It runs about one minute and covers every natural hazard and civil emergency the state uses the siren system for.1Hawai’i Emergency Management Agency. All-Hazard Statewide Outdoor Warning Siren System Its job is simple: get your attention so you go find out what is happening. The siren itself cannot distinguish a tsunami from a hurricane from a wildfire, which is why the follow-up information matters more than the sound.2Hawai’i Emergency Management Agency. News Release: Monthly Siren and Emergency Alert System Test for December 2025
Wavering Tone: Attack Warning Signal
The wavering tone, sometimes described as a wailing sound, historically meant one thing: an attack on the United States is imminent or already underway, and you should get to shelter immediately.3Hawai’i Emergency Management Agency. Monthly Siren and Emergency Alert System Test – November 2017 Hawaii reintroduced testing of this tone in December 2017 amid concerns about North Korean missile capability, but suspended its ballistic missile alert program after the false missile alert of January 2018.
What to Do When a Siren Sounds
If the siren is not a scheduled test, don’t ignore it, and don’t call 911 unless you are facing a life-threatening situation. Those lines need to stay open for people actively in danger. Instead, check these sources, in whatever order you can reach them fastest:
- Local radio or television, which carry Emergency Alert System messages
- Your phone, for a Wireless Emergency Alert with the specific threat and instructions
- Your county emergency management agency’s official social media accounts
The action you need to take depends entirely on the hazard. A hurricane warning calls for a different response than a tsunami warning, and the siren won’t tell you which one you’re dealing with.1Hawai’i Emergency Management Agency. All-Hazard Statewide Outdoor Warning Siren System
Tsunami Response, Because It’s the Most Common Real Use
Tsunami warnings are the most frequent real-world reason the sirens sound. If you are in a tsunami evacuation zone and officials issue an evacuation order, move inland and to higher ground immediately. Each county’s emergency management agency publishes evacuation zone maps, and it’s worth looking yours up before you ever hear a siren, especially if you are visiting or recently moved to the islands.4National Weather Service. Hawaii Tsunami Preparedness and Safety Information
If you cannot leave the evacuation zone in time, vertical evacuation is an option. A structural steel or reinforced concrete building of at least ten stories offers increased protection on the fourth floor or above. Stay at least 100 feet from inland waterways and marinas connected to the ocean, because wave surges travel up those channels.5Hawai’i Emergency Management Agency. Tsunami Evacuation Zones
Strong earthquake shaking that makes it hard to stand is itself a natural tsunami warning. Protect yourself during the shaking, then leave the evacuation zone as soon as it stops. Do not wait for a siren or an official alert.4National Weather Service. Hawaii Tsunami Preparedness and Safety Information
The Monthly Test
Hawaii tests its sirens on the first business day of every month at approximately 11:45 a.m. Only the steady Attention Alert Signal sounds, for about one minute, and no action is required.6Hawai’i Emergency Management Agency. Monthly Siren and Emergency Alert System Test for April 2026 The test runs alongside an Emergency Alert System check with local broadcast partners.
A siren at 11:45 a.m. on the first workday of the month is almost certainly the test. A siren at any other time, or one accompanied by a Wireless Emergency Alert on your phone, should be treated as real until you confirm otherwise.
Sign Up for County Alerts
The statewide sirens tell you something is wrong. County alert systems tell you what to do about it, with details about the hazard, road closures, evacuation orders, and shelter locations. Signing up takes a few minutes.
- Oahu (City and County of Honolulu): sign up at hnlalert.gov, or text HNLALERT to 888777 for text-only alerts.7City and County of Honolulu. Stay Informed – Department of Emergency Management
- Hawaiʻi County: uses the Everbridge system. Text HAWAIIALERTS to 888777 for text-only signup.8County of Hawaiʻi. Sign Up for Emergency Alerts
- Kauai County: uses the Wireless Emergency Notification System. Sign up online or call the Kauai Emergency Management Agency at (808) 241-1800.9Kauai County. Notification Services – Kauai County, HI
- Maui County: operates a county alert system with online registration through the Maui County Emergency Management Agency website.
Visitors on short trips can use the text-to-subscribe options and unsubscribe when they leave. Thirty seconds of setup gives you the detailed, localized follow-up that a siren alone can never carry.