Short answer
Storm surge is water pushed above the predicted tide by a storm, especially its winds. A tsunami is a wave series created by sudden displacement, often an undersea earthquake. Both can produce dangerous coastal flooding, and both require attention to official warnings; their causes and forecasts differ. 1 2
Both can flood coasts, but storm forcing and sudden displacement are different triggers.
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At a glance
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| Question | Storm surge | Tsunami |
|---|---|---|
| Trigger | Storm winds and related storm effects | Sudden water displacement |
| Typical association | Hurricane or other intense coastal storm | Earthquake, landslide or similar event |
| Relation to tide | Measured above predicted tide | Can arrive at any tide stage |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Storm surge. Abnormal coastal water-level rise generated by a storm, above the predicted astronomical tide. 1
Tsunami. A series of long waves produced by sudden displacement of a large body of water. 2
Key differences
Surge is a sustained rise in coastal water level associated with a storm system; the actual storm tide includes astronomical tide plus surge. A tsunami propagates as long waves after displaced water begins moving. Ordinary breaking waves can ride on top of either phenomenon and add impact. 1 2
How to tell them apart
Ask what triggered the unusual water. A forecast hurricane with onshore winds suggests surge; a major offshore earthquake and tsunami alert suggests tsunami. Follow official local evacuation instructions rather than trying to diagnose the hazard from a shoreline view. 1 2
Where they overlap
Both can inundate low coastal land, damage infrastructure and create strong currents. A high astronomical tide can worsen either outcome at a particular time. 1 2
Edge cases
A storm can generate multiple coastal hazards at once, including wind waves and surge. A tsunami may look like a rapid surge near shore, so appearance alone can mislead. Tsunami waves may arrive in several pulses, and the first need not be largest. 1 2
Why the distinction exists
The distinction helps forecasters and residents connect a warning to its physical cause and likely timing. The right term is also essential for interpreting storm-tide forecasts versus tsunami alerts. 1 2
Common misconceptions
Storm surge is not a tsunami caused by wind, and a tsunami is not an extreme astronomical tide. 1 2
Examples
A hurricane pushes seawater landward above the expected tide: storm surge. An undersea earthquake displaces water and sends a wave series to the same coast: tsunami. 1 2
Sources
Sources checked October 3, 2026.
- National Hurricane Center — Storm Surge Overview. Storm surge definition.
- NOAA National Ocean Service — What is a tsunami?. Definition.