What Is a Storm Surge?

Medically Reviewed by Neha Pathak, MD on September 28, 2022

A storm surge is an abnormal and temporary rise in the water level that's caused by a storm. It causes water to reach above regular tides. Storm surges become dangerous when a storm (usually a hurricane or tropical storm) reaches land. Storm surges can lead to intense flooding in coastal communities.

A storm surge can be the most dangerous part of a hurricane or tropical storm in terms of property damage and loss of  life on the coastline.

Storm surges are different from storm tides. A storm tide is when the water level rises because of a storm surge and the regular high tide. These can create water levels 20 feet or more above the regular level.


What Happens During a Storm Surge?

When the sea level rises underneath a storm, the water is unable to escape anywhere but land once it reaches the shore. Once the water reaches land, it can cause floods or other forms of hurricane damage.

Some examples of storm surge damage include:

  • Strong waves and currents that cause land and buildings to break down
  • Saltwater that gets into freshwater lakes, aquifers, or streams (which can harm animals and make your drinking water dangerous)
  • Harm to other habitats
  • Damage to transportation systems (such as airports, ports, harbors, roads, railroads, bridges, and tunnels)
  • Threats to human life, safety, and health

The intensity of a storm surge can differ. There are a few factors that help project how bad a storm surge will be. They include:

Wind. During a hurricane or tropical storm, seawater gets pushed together at the center of the storm. If the wind is faster, it's able to collect more water. The speed of wind determines the category of a hurricane, so a higher category means a larger mound of water.

Low air pressure. In the center of a hurricane, air pressure is low. This causes a small budge in the ocean. This adds to the buildup of water that creates a storm surge. While most of a storm surge is caused by wind, low air pressure can make it slightly more intense.

The shape of the coastline. If a coast curves inward, it's more likely to have large storm surges than ones that curve outward. If there's a bay in your area, you may be at a higher risk for storm surges. This is because the mound of water might get funneled into the small area.

The hurricane's speed. If a hurricane moves fast, it can lead to more storm surge on coastlines that are straight. But if a storm moves slow, they tend to cause more storm surge in coastal areas with estuaries and bays.

The shape of the seafloor. If you live in a coastal area that has shallow seafloor, you're more likely to get large storm surges than coastal areas near deep seafloors.

The direction of the hurricane. If a hurricane heads toward a coastline straight on, it's more likely to cause a large storm surge than if the hurricane hit the coast at an angle or parallel to the coast.

Who's Most at Risk for a Storm Surge?

Around 22 million people along the United States East Coast and Gulf Coast can be affected by storm surges.

Areas near the coast are at the highest risk for storm surges because they live closest to where the water will begin to flood.

Low-lying islands and coastal communities with land that isn't much higher than sea level are especially at risk for this.



How Can You Prepare for a Storm Surge?

Certain computer models, like the National Weather Service SLOSH (sea, lake, and overland surges from hurricanes) model take many things into account to predict storm patterns. Weather forcasters will share this information to help you prepare for the severity of a storm. Experts will be able to guess how a storm surge will affect specific coasts with this tool.

It's important to pay attention to these forecasts to understand how a storm surge could affect you. To be prepared during a hurricane or tropical storm, it's a good idea to:

Understand what the forecasts mean. A weather forecast doesn't mean much if you don't understand what it's saying. Learn the different terms, such as hurricane watch versus hurricane warning.

Make an evacuation plan. Decide how much at risk you and your loved ones are based on the area that you live in. If you're in an evacuation zone, have a plan for where you'll go.

Create a disaster kit. No matter if you decide to stay or evacuate, you'll want to prepare a disaster kit. Consider essential food, water, clothes, medications, or other needs.

Learn about insurance for hurricanes and floods. Once you've made sure you and your loved ones are safe, it's important to look after your property. Look into insurance options in case a storm surge damages your house. Even a small amount of water can cause a lot of damage.





How Can You Recover From a Storm Surge?

After a storm surge, you'll want to take the steps to stay safe. Some guidelines to keep you and your family out of trouble include:

  • Be careful on your way home and during cleanup. Avoid debris or damaged buildings.
  • Look into helpful government programs. These can help support you with housing issues, food needs, and other necessities.
  • Plan for future disasters and understand how you can be ready for future storm surge issues.


Show Sources


National Hurricane Center and Central Pacific Hurricane Center: "Storm Surge Overview."

Center for Science Education: "What Causes Storm Surge?"

National Environmental Education Foundation: "The Empowered Storm Surge," "Preparing for Hurricane Season." "Five Tips to Recover After a Hurricane."



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