Preparing for a tsunami means knowing the warning signs, having an evacuation plan before you need one, and keeping a go bag ready at all times. If you live in or visit a coastal area with tsunami risk, your target during an evacuation is to reach ground at least 100 feet above sea level or travel 2 miles inland from the coastline. Everything else in your preparation supports getting you and your family to that point quickly.
Recognizing Natural Warning Signs
Official alert systems don’t always beat the wave. For tsunamis triggered by nearby earthquakes, you may have only minutes before the first surge arrives, and natural signs could be your earliest warning. Four signals should trigger immediate evacuation:
- A long or violent earthquake. Any earthquake lasting 20 seconds or more near the coast, or one strong enough to knock you off your feet, can generate a tsunami. Don’t wait for an official alert. Once the shaking stops, move to high ground immediately.
- Unusual changes in water level. A rapid, dramatic drop in the ocean (exposing the seafloor) or a sudden rise that doesn’t match the tide is one of the most recognizable tsunami precursors. If the water pulls back far and fast, you have very little time.
- A loud roar from the ocean. Some survivors describe hearing a sound like a freight train or jet engine coming from the water before the wave arrived.
Any one of these signs is enough reason to evacuate. You do not need confirmation from a phone alert or siren. During the shaking itself, drop, cover, and hold on first, then move to higher ground as soon as it’s safe to walk.
Understanding Official Tsunami Alerts
The National Tsunami Warning Center issues four levels of alerts, and each one calls for a different response. Knowing the difference keeps you from either ignoring a real threat or panicking over a routine notification.
A Tsunami Warning is the most serious. It means dangerous coastal flooding is imminent, expected, or already happening. Move to high ground or inland immediately. Powerful currents and flooding can continue for hours after the first wave.
A Tsunami Advisory means strong currents and waves dangerous to anyone in or near the water are expected, but widespread flooding of land is not. Stay out of the ocean, off beaches, and away from harbors and marinas.
A Tsunami Watch means a tsunami may later affect your area. No evacuation is needed yet, but you should stay alert, check for updates, and be ready to act quickly if the watch is upgraded to a warning.
A Tsunami Information Statement is issued after an earthquake to let you know there is no threat of a destructive tsunami. No action is needed.
You can receive these alerts through Wireless Emergency Alerts on your phone, NOAA Weather Radio, local sirens (in many coastal communities), and local news. Having more than one way to receive alerts matters because any single system can fail.
Building Your Evacuation Plan
The core of tsunami preparedness is a plan you’ve practiced before you need it. Start by checking whether you live, work, or vacation in a tsunami hazard zone. The National Weather Service maintains a directory of tsunami evacuation and inundation maps organized by state and territory at weather.gov. States including Alaska, California, Hawaii, Oregon, and Washington all provide detailed maps showing which areas would flood and which routes lead to safety. Many communities also post physical evacuation route signs along coastal roads.
Once you know whether your location falls within an inundation zone, identify at least two evacuation routes to high ground or inland areas. Your primary goal is to reach terrain 100 feet above sea level or get at least 2 miles from the coastline. If you can’t reach either threshold, go as high or as far as you can. Plan routes from every place you spend significant time: your home, workplace, children’s school, and favorite beach spots.
Practice the routes on foot. Tsunamis from nearby earthquakes can arrive in minutes, and roads may be blocked by earthquake damage, downed power lines, or gridlocked traffic. Walking or running is often faster and more reliable than driving. Time your practice walks so you know exactly how long each route takes.
If you have family members who would be in different locations during the day, agree on a meeting point on high ground and a communication plan so you’re not searching for each other in the hazard zone.
When High Ground Isn’t Reachable
Some coastal communities, particularly in the Pacific Northwest, sit in flat areas where high ground is miles away. In these locations, vertical evacuation structures offer an alternative. These are specially engineered buildings designed to survive both the earthquake and the tsunami that follows. They must withstand aftershocks, 12 to 24 or more hours of repeated wave surges, ground liquefaction, and the impact of floating debris.
Not every tall building qualifies. Designated vertical evacuation structures are built or retrofitted to specific engineering standards, with their safe floor level calculated using tsunami modeling for that exact location. The building code requires adding a 30 percent safety margin to the modeled wave height, plus an extra 10 feet, to determine the minimum refuge floor. Check with your local emergency management office to find out whether your community has designated vertical evacuation sites and where they are. If your area has one, include it in your evacuation plan as an option when reaching higher terrain isn’t possible in time.
Packing a Go Bag
Your go bag should be packed and stored where you can grab it in under a minute. Use a duffel bag or small backpack that’s easy to carry while walking or running. Store items in airtight plastic bags inside the container to protect them from water.
Focus on what you’d need for 72 hours away from home:
- Water and food. One gallon of water per person per day and non-perishable food that doesn’t require cooking.
- Medications. A three-day supply of any prescriptions, plus basic first aid supplies.
- Documents. Copies of IDs, insurance policies, and bank information stored in a waterproof container or saved on a USB drive in a sealed bag.
- Light and communication. A flashlight with extra batteries, a battery-powered or hand-crank radio for receiving NOAA alerts, and a portable phone charger.
- Cash. Small bills, since ATMs and card readers may be down.
- Matches in a waterproof container and a whistle for signaling rescuers.
If you have young children, elderly family members, or pets, tailor the bag to their needs: formula, diapers, extra glasses, pet food, leashes.
What to Do If You’re on a Boat
Tsunami safety for boaters depends on where you are when the warning comes. If you’re already at sea and have time, head for deep water. The National Tsunami Hazard Mitigation Program recommends reaching a minimum depth of 50 to 100 fathoms (300 to 600 feet) to be safe from a local tsunami, and staying at least half a mile from shore or any fringing reef. Specific guidance varies by region. Along California, Oregon, Alaska, and Washington, vessels at sea should aim for 100 fathoms for local-source tsunamis, while 30 fathoms is considered sufficient for distant-source events when the ship is still in harbor with time to move.
If you’re docked in a harbor or marina and receive a warning, the safest choice in most cases is to abandon the vessel and evacuate on foot to high ground. Trying to motor out of a congested harbor takes time you may not have, and harbors become especially dangerous as tsunami currents accelerate through narrow channels.
After the First Wave
One of the most dangerous misconceptions about tsunamis is that the event is over after the first wave. Tsunamis are a series of surges that can last for hours or even days. Unlike wind-driven ocean waves that arrive every 10 to 20 seconds, tsunami surges can be many minutes apart, and more than an hour can pass between successive crests. The first wave is not always the largest.
Stay on high ground until local authorities issue an all-clear. Returning to the coast too soon is one of the leading causes of tsunami casualties worldwide. Dangerous currents persist long after the most visible flooding has receded, and later surges can arrive with little additional warning. Monitor your NOAA radio or local emergency channels for updates, and treat the event as ongoing until you hear an official announcement that it’s safe to return.