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What Is a King Tide?

A "king tide" isn't a scientific term for a special kind of tide — it's the everyday name for the highest tides of the year, and in low-lying areas they can cause real flooding.

The short definition

A king tide is an especially large spring tide, occurring when the moon's and earth's elliptical orbits bring them closest to each other (perigee) at the same time as a new or full moon. That alignment pushes an already-large spring tide even higher than usual, typically a few times a year at a given location.

Why they can cause flooding

In low-lying coastal areas, a king tide alone can push water into streets, parking lots, and low properties that normally stay dry, even without any storm involved. If a king tide coincides with heavy rain, onshore wind, or low atmospheric pressure, the flooding can be significantly worse — this combination is sometimes called "sunny day flooding" when it happens without a storm.

King tide vs. storm surge

These are different things that can stack on top of each other. A king tide is a predictable, astronomical event you can see coming weeks in advance on a tide chart. Storm surge is water pushed up by a storm's wind and low pressure, on top of whatever the tide happens to be doing. A storm arriving during a king tide is a worst-case combination for coastal flooding.

How to check if one's coming

Because king tides are predictable, they show up clearly on a standard tide chart as the highest highs of the month or year for your station. Check the tide chart for your area, and pay extra attention to the predicted height, not just the time, around new and full moons in the months your area historically sees the highest tides.