A tsunami warning means dangerous coastal flooding and powerful currents may be imminent or occurring; move to high ground or inland. A tsunami advisory means dangerous currents or waves are possible near the water, but significant inundation is not expected; stay out of the water and away from beaches and waterways. A tsunami watch means the area may be affected later, while the local danger is still undetermined; stay informed and be ready to act.
The three U.S. tsunami alerts at a glance
The U.S. Tsunami Warning Centers use warning, advisory and watch to communicate different combinations of hazard, timing and required action. They are not simply three confidence levels for one forecast. A warning calls for immediate protective movement, an advisory restricts access to the water, and a watch gives you time to monitor information and prepare while analysts determine whether the area will be affected. The official definitions are published by the U.S. Tsunami Warning Centers.
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| Alert | What it means for the area | Immediate public action |
|---|---|---|
| Warning | A tsunami capable of dangerous coastal flooding and powerful currents is imminent, expected or occurring. Widespread inundation is possible. | Move to high ground or inland and follow local evacuation instructions. |
| Advisory | Strong currents or waves dangerous to people in or very near the water are possible. Significant inundation is not expected in advisory areas. | Stay out of the water and away from beaches, harbors, rivers and other waterways. |
| Watch | A tsunami may later affect the area, but the danger level there has not yet been determined. | Stay informed, review your route and be prepared to act if the message changes. |
Warning: leave the hazard zone
A warning is the highest-action U.S. tsunami message. It covers the possibility of destructive coastal flooding as well as currents strong enough to sweep people, vehicles or vessels away. The wording “imminent, expected or occurring” means the center may be dealing with a tsunami that has already been observed, one forecast to arrive soon, or one judged sufficiently likely that waiting for more confirmation would create unacceptable risk.
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Advisory: the water is dangerous even without major flooding
An advisory is narrower than a warning but is not a “minor” version of one. Waves and currents can be hazardous at beaches, jetties, marinas, river mouths and other connected waterways even when significant inland flooding is not expected. The danger can persist after the first wave because successive waves and changing currents may vary in strength.
Leave the water and stay away from the shoreline and waterways covered by local instructions. Do not surf, swim, fish from exposed structures, launch a boat or approach a harbor to watch conditions. Follow any closures or access restrictions issued by local authorities.
Watch: possible later impact, decision still developing
A watch identifies an area that could be affected while the threat is being evaluated. It does not mean that a tsunami will definitely arrive, and it does not authorize you to ignore a later update. Analysts may still be assessing the earthquake, sea-level observations and forecast information.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallDuring a watch, keep a phone, radio or other official information source available; check where you would go if an evacuation became necessary; account for children, older adults, visitors, pets and anyone who needs assistance; and be ready to follow a new local instruction without delay. Do not evacuate solely because a watch appears on a map unless local emergency officials tell you to do so.
How an alert can change
Warning centers often issue a watch early, before a destructive tsunami is confirmed. They then combine seismic analysis, tide-gauge and other water-level observations, and forecast information. The message can be upgraded to a warning, changed to an advisory, adjusted to cover a different coastline, or canceled as evidence develops. A watch therefore describes the current state of knowledge, not a guaranteed sequence that every event follows.
An area can move directly from an information statement to an advisory or warning, or a watch can be canceled without either. Read the newest message rather than relying on the first label you saw in a social-media post, text notification or news report. Current messages and timestamps are available through Tsunami.gov’s message definitions and products and local emergency channels.
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What an information statement means
An information statement reports an earthquake or other tsunami-related event of interest. In most cases it indicates that a destructive basin-wide tsunami threat is not expected and helps prevent unnecessary evacuations. It is not a promise that no local effects are possible forever: later analysis can produce a watch, advisory or warning.
Read the entire statement, including its region, issue time and update instructions. If you are in a coastal hazard zone and feel a strong or long earthquake, see unusual water behavior or hear an ocean roar, act on those natural signs even if an information statement—or no official message—has reached you.
What to do for each alert
If your area is under a warning
- Move immediately. Go to high ground or inland, using the route identified in your community’s evacuation plan.
- Follow local directions. Police, fire departments and emergency managers may close roads, open shelters or define a boundary that is more specific than the national message.
- Keep moving away from the coast. Do not stop at beaches, overlooks, bridges, river mouths or harbors to watch the waves.
- Stay informed while relocating. Monitor official updates in case the affected area, route or shelter information changes.
- Remain in the safe location until local officials say it is safe. A later cancellation from a warning center reflects its assessment of the threat, but the final decision that your particular area is safe belongs to local and state emergency management officials.
If your area is under an advisory
- Exit the water and waterfront immediately. Leave beaches, docks, breakwaters, marinas and low-lying waterways included in local instructions.
- Keep people and equipment away from moving water. Strong currents can injure someone standing on a shoreline or pier even when no flood wave reaches nearby streets.
- Do not launch or retrieve boats unless authorities direct it. Harbor entrances and channels can become dangerous as currents change.
- Watch for updates. An advisory can be expanded, reduced, upgraded to a warning or canceled.
If your area is under a watch
- Confirm the affected location and issue time. A watch may cover only particular coastlines or may be revised as forecasts improve.
- Prepare to leave. Identify high ground or an inland destination, check transportation options and gather essential medication, identification and communication equipment.
- Notify people who may need help. Make a plan for children, older adults, people with disabilities, visitors and pets before roads become crowded.
- Keep monitoring official sources. Be ready to follow an advisory or warning instruction immediately, or to stand down if the watch is canceled.
Natural warnings can come before an official message
The U.S. Tsunami Warning Centers describe two broad ways people receive a warning: official messages and natural warnings. You may not receive both. In a tsunami hazard zone, treat any of these natural signs as an immediate reason to move inland or to high ground:
- Strong or unusually long earthquake shaking.
- A loud roar or rumble from the ocean.
- The sea suddenly pulling back or rising unusually fast.
These signs matter because a nearby, or “local,” tsunami can reach the coast before an official alert is disseminated. Do not wait for a siren, phone notification or confirmation from a website. Once you are safe, look for official instructions and help others if doing so does not delay your evacuation. The warning-center FAQ explains natural and official warnings at Tsunami.gov’s tsunami FAQ.
How official alerts reach people in the United States
There is no single channel that reaches everyone in every location. Depending on your community and the event, official information may be broadcast through:
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- Local radio and television.
- Marine radio.
- Wireless Emergency Alerts on compatible mobile devices.
- NOAA Weather Radio.
- NOAA websites, including Tsunami.gov.
- Official social-media accounts.
- Outdoor sirens and local emergency-notification systems.
Use more than one way to receive updates when possible, and continue monitoring after the first alert. A NOAA Weather Radio can be a useful dedicated source, particularly when cellular service or electricity is unreliable, but it is supplemental rather than mandatory or sufficient by itself. The official FAQ lists it alongside the other delivery methods and stresses that people must also respond to natural warning signs.
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Which warning center serves which coast?
The alert system described here is the domestic U.S. system for U.S. and Canadian coastlines and the British Virgin Islands. The two U.S. centers have different primary service areas:
| Center | Primary responsibility |
|---|---|
| National Tsunami Warning Center | Continental United States, Alaska and Canada. |
| Pacific Tsunami Warning Center | Hawaii, U.S. Pacific and Caribbean territories, and the British Virgin Islands. |
For international Pacific and Caribbean events, messages from the centers can provide guidance to national authorities. Each country decides which alert level to issue for its own coastline. Other countries may use different names, thresholds or color systems, so do not assume that an overseas “watch,” “warning” or “advisory” has exactly the U.S. meaning.
U.S. territories should use messages specifically issued for their regions. If you are traveling, check the local emergency-management authority rather than translating a U.S. label onto another country’s system.
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How to read a tsunami alert map
A highlighted forecast zone shows where the warning center is evaluating or forecasting effects. It is not the same as the modeled inundation area and is not automatically an evacuation boundary. A highlighted zone can extend inland beyond the places expected to flood, while a local evacuation plan may use roads, landmarks or elevation lines that are not visible on the national map.
Use the map to identify the message’s geographic scope, then use local emergency management, law enforcement or the relevant National Weather Service forecast office for the instruction that applies to your address. When a map and a local order appear inconsistent, follow the current instruction from local officials and seek clarification rather than guessing.
Reading the wording and timestamps
Every message has a geographic scope and an issue time. Those details matter as much as the bold alert label. A warning for one coastline does not automatically apply to every nearby shore, and a later update may add or remove locations. Compare the newest message with the one you first received, especially if it came through a reposted screenshot or a notification that does not display the full text.
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The action language is deliberately practical: a warning tells people to move to high ground or inland, an advisory tells people to stay out of the water and away from beaches and waterways, and a watch tells people to remain informed and prepared. If a local emergency manager gives more specific directions—such as a route, closure or shelter instruction—use those directions for your location.
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Why local officials have the final say
The warning centers evaluate the tsunami threat and issue, update or cancel national messages. Local and state emergency-management officials apply that information to streets, neighborhoods, evacuation zones and shelters. Their decisions account for local geography and public-safety operations that a national message cannot describe in detail.
That is why cancellation does not necessarily mean you should immediately return to a beach or waterfront. The warning center’s cancellation reflects its evaluation of the tsunami threat, while local officials decide when a particular area is safe to re-enter. Continue following local instructions until they change.
Common mistakes to avoid
- Treating a watch as a prediction of certain impact. It means impact is possible and the danger level is not yet known.
- Assuming an advisory is harmless. Dangerous currents can injure or kill people in or very near the water without widespread flooding.
- Waiting for an official alert after natural signs. Strong shaking, an ocean roar or sudden water movement requires immediate action in a hazard zone.
- Returning after the first wave. Wait for local officials to declare the area safe; waves and currents can continue changing.
- Using an old screenshot or post. Alerts can be geographically revised, upgraded, downgraded or canceled, so check the latest official message and its issue time.
- Equating a colored map with an evacuation order. The map’s highlighted forecast zone and the local inundation or evacuation boundary serve different purposes.
- Assuming every country uses the same labels. National authorities set their own public alert categories outside the U.S. domestic system.
A practical preparedness checklist
Preparation is most useful before a watch appears. Keep this short checklist with your household or travel plan:
- Know whether your home, workplace, school or lodging is in a tsunami hazard zone.
- Identify a route to high ground or inland, and practice it on foot if local guidance recommends doing so.
- List people, pets and mobility needs that require assistance.
- Choose at least two ways to receive official information, such as local notifications plus radio or NOAA Weather Radio.
- Save the official tsunami information page and your local emergency-management contact.
- During an earthquake or natural warning, leave first and seek updates after reaching safety.
Bottom line
Remember the action attached to each U.S. label: warning means move away from the coast; advisory means stay out of the water and away from waterways; watch means monitor information and be ready to act. Any label can change as evidence arrives, and natural signs can require immediate evacuation before an official message. For a live event, rely on the current message from the appropriate warning center and the instructions of local emergency officials.
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Does a tsunami watch mean I should evacuate?
Not by itself. A watch means the area may be affected later, but the danger level is not yet determined. Stay informed, review your evacuation route and be ready to act. Evacuate when local emergency officials direct you to do so, or immediately if you are in a hazard zone and experience natural warning signs such as strong or long shaking, an ocean roar, or unusual water movement.
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Is a tsunami advisory safe for people on the beach?
No. An advisory means dangerous waves or currents are possible for people in or very near the water, even though significant inundation is not expected in advisory areas. Stay out of the water and away from beaches, harbors, rivers, marinas, jetties and other connected waterways until local officials change the instruction.
Can a watch be canceled without becoming a warning?
Yes. A watch may be upgraded to a warning or advisory, adjusted geographically, or canceled as seismic, water-level and forecast information develops. The labels do not describe a guaranteed sequence, so always read the latest message rather than assuming the next step.
What should I do if I feel an earthquake but receive no alert?
In a tsunami hazard zone, strong or unusually long shaking is a natural warning. Move immediately to high ground or inland; do not wait for a siren, phone notification or website update. Once safe, monitor official information and follow local instructions.
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Not necessarily. Cancellation reflects the warning center’s evaluation of the tsunami threat. Local and state emergency-management officials make the final decision that a particular area is safe, so remain away until they lift local restrictions or give a return instruction.
Why is my location highlighted on a tsunami map if it is not expected to flood?
A highlighted forecast zone is the area being evaluated or forecast for effects. It is not identical to the modeled inundation area and is not automatically an evacuation boundary. Use local emergency management, law enforcement or the relevant National Weather Service forecast office for instructions that apply to your address.
Do all countries use the same tsunami alert categories?
No. The warning, advisory and watch definitions in this article describe the domestic U.S. system for U.S. and Canadian coastlines and the British Virgin Islands. International messages can guide national authorities, but each country decides which labels, thresholds or color systems to use for its own coastline.
What is the best way to receive tsunami alerts?
Use more than one official channel when possible. Depending on the community, alerts may come through local radio and television, marine radio, Wireless Emergency Alerts, NOAA Weather Radio, NOAA websites such as Tsunami.gov, official social-media accounts, outdoor sirens and local notification systems. No channel replaces responding to natural warning signs.
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Warning: move to high ground or inland. Advisory: stay out of the water and away from beaches and waterways. Watch: stay informed and be ready to act. Follow the latest message and local emergency officials, and act immediately on natural warning signs.
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