Hurricane Storm Surge Estimator
Estimate storm surge height from hurricane category and coastal geometry.
Understand surge risk by Saffir-Simpson category for coastal planning.
Storm surge is an abnormal rise of water generated by a hurricane’s winds pushing ocean water toward shore. It is the deadliest hurricane hazard, responsible for roughly half of all hurricane-related deaths in the United States.
Storm surge vs. storm tide:
- Storm surge: the rise above the normal astronomical tide, which is the part the storm itself creates
- Storm tide: storm surge plus the normal tide, which is the total depth of water at the shore
That distinction is not pedantry. The same surge arriving six hours later can be several feet shallower simply because the tide has gone out.
Saffir-Simpson categories and typical surge heights. The wind ranges here are the current National Hurricane Center values, which shifted slightly when the scale was revised in 2012:
| Category | Sustained winds | Typical surge |
|---|---|---|
| Tropical Storm | 39 to 73 mph | 1 to 2 ft (0.3 to 0.6 m) |
| Category 1 | 74 to 95 mph | 4 to 5 ft (1.2 to 1.5 m) |
| Category 2 | 96 to 110 mph | 6 to 8 ft (1.8 to 2.4 m) |
| Category 3 | 111 to 129 mph | 9 to 12 ft (2.7 to 3.7 m) |
| Category 4 | 130 to 156 mph | 13 to 18 ft (4.0 to 5.5 m) |
| Category 5 | 157 mph and above | 18 to 25 ft (5.5 to 7.6 m) |
The category is a wind scale, not a surge scale, and treating it as one has killed people. Sandy came ashore in 2012 as a post-tropical storm with Category 1 winds and pushed a 9 ft surge into New York harbour because it was enormous and hit at high tide. Charley in 2004 was a Category 4 and produced only about 6 ft, because it was small and fast.
What actually sets the height:
- Coastal geometry: shallow bays and funnel-shaped estuaries concentrate water and amplify surge
- Angle of approach: a perpendicular landfall drives far more water ashore than a glancing pass
- Storm size: a broad, slow storm has time to pile water up. Radius matters more than peak wind
- Bathymetry: a wide, shallow continental shelf, as along the Gulf coast, roughly doubles surge for the same storm
Historic examples: Katrina (2005) produced about 28 ft near Pass Christian, Mississippi, the highest measured in the US. Ike (2008) pushed 20 ft over the Bolivar Peninsula. Michael (2018) drove 14 ft into Mexico Beach, Florida.
Evacuation zones: US coastal counties use lettered zones (A, B, C and so on) drawn from surge modelling rather than from category. Zone A evacuates for a Category 1 threat. Follow the official order. No property is worth a life, and surge is what does the killing.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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