Storm Surge
Storm surge is an abnormal rise in sea level during a hurricane or other intense storm, measured as the height of the water above the normal predicted tide. It is produced mainly by the storm's winds pushing water toward the shore. Storm surge is the leading cause of deaths from hurricanes.
Why It Matters
Water is heavy: a cubic yard weighs about 1,700 pounds, so moving surge water batters buildings as well as flooding them. Surge on top of the normal tide is called storm tide, which can reach 20 feet or more when the surge arrives at high tide, with waves adding to the water level.
Storm Surge Terms and Alerts
| Term | Meaning |
|---|---|
| Storm surge | The rise in sea level caused by the storm, above the level the tide alone would produce |
| Storm tide | The total water level: storm surge plus the astronomical tide |
| Storm Surge Watch | Life-threatening flooding from rising water moving inland is possible, generally within 48 hours |
| Storm Surge Warning | There is a danger of life-threatening flooding from rising water moving inland, generally within 36 hours |
What Makes Surge Higher
- Storm intensity: stronger winds push more water.
- Size: a larger storm produces a higher surge.
- Forward speed: a faster storm produces a higher surge at the open coast, while a slower storm pushes water farther inland.
- Angle of approach: a storm moving straight onshore is more likely to produce a higher surge than one moving parallel to the coast.
- Shape of the coast: a concave coastline, such as a bay, produces a higher surge than a convex one.
- Slope of the sea floor: a wide, gently sloping continental shelf allows a higher surge than a narrow, steep one.
Common Misconceptions
- The hurricane category does not tell you the surge. The Saffir-Simpson scale is based on wind speed only and does not account for storm surge.
- Storm surge is not the same as storm tide. Surge is the storm's contribution, and storm tide is the total water level once the normal tide is included.
Frequently Asked Questions
What is the difference between storm surge and storm tide?
Storm surge is the rise in water caused by the storm alone, above the predicted tide. Storm tide is the total water level: the storm surge plus the astronomical tide. A surge arriving at high tide produces a higher storm tide than the same surge at low tide.
Does a higher hurricane category mean a higher storm surge?
Not reliably. Stronger winds do produce a higher surge, but so do a larger storm, a shallow sloping sea floor, and a concave coastline. The Saffir-Simpson category measures wind speed only and does not account for surge.
What is a Storm Surge Warning?
It means there is a danger of life-threatening flooding from rising water moving inland from the shoreline, generally within 36 hours. A Storm Surge Watch means that flooding is possible, generally within 48 hours.
Related Terms
Hurricane
A tropical cyclone with maximum one-minute sustained surface winds of 74 mph or greater in the Atlantic or eastern and central North Pacific. Hurricanes are categorized 1-5 on the Saffir-Simpson Hurricane Wind Scale, with Category 5 beginning at 157 mph.
Saffir-Simpson Scale
The Saffir-Simpson Hurricane Wind Scale rates hurricanes from Category 1 to Category 5 by maximum sustained wind speed. Category 1 starts at 74 mph and Category 5 at 157 mph, and Category 3 and higher are called major hurricanes. The scale measures wind only: it does not account for storm surge, rainfall flooding, or tornadoes.
Eye Wall
The ring of intense thunderstorms surrounding a hurricane's eye, containing the storm's strongest winds and heaviest rainfall. Eye wall replacement cycles can temporarily weaken a hurricane before it potentially re-intensifies.
King Tide
King tide is a popular, non-scientific name for an exceptionally high tide. King tides happen when the higher tides around a new or full moon coincide with the Moon's closest approach to Earth, called perigee. They can flood low-lying coastal areas on a clear day, and they raise the water level any storm surge is added to.
Tropical Storm
A tropical cyclone with maximum sustained winds between 39-73 mph. At this stage, the storm receives a name. Tropical storms can produce dangerous flooding, winds, and tornadoes even without reaching hurricane strength.
Post-Tropical Cyclone
A post-tropical cyclone is a former tropical cyclone that no longer has enough tropical characteristics to be classified as one. It can still bring heavy rain and strong winds. The two kinds are extratropical cyclones, which draw their energy from temperature contrasts between air masses, and remnant lows, which have winds below 34 knots (39 mph).
Storm Surge: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
In-depth guide
What Is Storm Surge? Surge vs Storm Tide, and Why Category Doesn't Predict It
Storm surge explained: how surge, storm tide, and inundation differ, what decides how high the water gets, why a Category 2 can flood worse than a Category 4, and which NHC products to act on.
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Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Guide
Hurricane Categories Explained
Understand what each Saffir-Simpson category says and what it does not say about a storm's risk.
Seasonal Hub
Hurricane Season Guide
Track tropical risk, categories, and preparedness advice in one place.
Feature
Hurricane Tracker
Track cones, watches, warnings, and tropical systems from formation through landfall.
Guide
The Hurricane Cone of Uncertainty
What the cone really means, why impacts reach far outside it, and how to read spaghetti models.
Sources
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Tornado
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In the WeatherAI App
WeatherAI's Tropical Weather Hub follows NHC-tracked storms with forecast tracks, cones, and watches and warnings, and Storm Surge Watches and Warnings appear among the tropical alerts for a U.S. location.
Availability, coverage, update frequency, and alert delivery vary by data source, region, subscription plan, device permissions, and service conditions. WeatherAI supplements official sources and is not an emergency notification service. For life-safety decisions, rely on your national weather service, local emergency management, and official warning channels.