A king tide is an informal name for the very highest (and often lowest) tides of the year — the days when the water reaches further up the beach than on any normal high tide, and pulls back further than usual a few hours later. It's not a different kind of tide, just the far end of the normal range.
The short answer
Tides rise and fall because the moon and sun pull on the oceans. Most months swing between moderate highs and moderate lows. A few times a year, several astronomical factors line up at once and the swing gets dramatically bigger. Those peak days are what people call king tides. On the US Atlantic and Pacific coasts, a king high tide can run a foot or more above an average high — enough to put seawater on roads that stay dry the rest of the year.
What causes a king tide
Three ingredients have to coincide:
- A new or full moon. When the sun and moon align, their gravitational pulls add together, producing the larger-than-average spring tides that arrive every two weeks.
- Perigee. The moon's orbit is an ellipse, and once a month it passes closest to Earth (perigee). A closer moon pulls harder — a spring tide that lands on perigee is called a perigean spring tide, which is the technical term behind most "king tides."
- Seasonal factors. In many places the biggest kings come in winter or fall, when seasonal winds, currents, and water temperatures already bias sea level upward.
When a perigean spring tide meets a storm or strong onshore wind, you get the photos that make the news: water over sea walls, flooded parking lots, waves where there is usually promenade.
King tide vs. storm surge
People often confuse the two, and the difference matters. A king tide is pure astronomy: it appears in the predictions years in advance, arrives on schedule, and leaves on schedule. A storm surge is weather: wind piling water against the coast and low pressure lifting it further, arriving with a storm and often without much warning. The dangerous compound event is a storm surge that peaks during a king high tide — the same water level that would be a nuisance on a normal tide becomes a flood on a king tide. That's why emergency managers watch king tide calendars when they read storm forecasts, and why you should treat a king tide forecast as a heads-up, not a show scheduled for your convenience.
When king tides happen
Because they follow the moon, king tides are predictable to the minute. They always fall within a day or two of a new or full moon that coincides with perigee — typically three to four clusters a year on each coast. Right now, the next full moon is on2026-11-24 and the next new moon on 2026-12-08; the spring tides around those dates are the ones to watch, and if either falls near perigee, that's a king tide window. Your local tide chart shows the effect directly: look for the days with the biggest tidal range of the month.
Why king tides matter
For most people, a king tide is a curiosity — a dramatic day at the beach. But they serve two serious purposes:
- A preview of sea level rise. Coastal communities photograph king tides precisely because they show what "normal" high water may look like a few decades from now. If a road floods only during king tides today, it may flood monthly by mid-century.
- Planning. Dock builders, surveyors, and engineers use king tide levels as an informal benchmark for how high structures really need to sit.
For anglers and beachgoers the same days have a silver lining: the matching lowtides are the lowest of the year, exposing reefs, sandbars, and tide pools that stay underwater the rest of the time.
Documenting a king tide
Several state programs and universities run king tide photo projects, and they genuinely want your snapshots. The useful protocol is simple: photograph the same recognizable spot — a dock piling, a stair, a sea wall mark — at the king high tide and again at an ordinary high tide, note the date, time, and exact location, and submit through the project's site or app. A photo with a fixed reference point lets researchers convert "wow, look at that" into an actual water-level measurement, and those measurements feed directly into local flood maps and sea-level planning. It's one of the few cases where standing at the water's edge with your phone counts as field research — just do it from dry ground.
Watching one safely
King tide days compress a lot of water movement into a few hours. If you go to watch or to explore the extreme low tide, keep two rules: never turn your back on an incoming king tide (it rises faster than a normal tide and can cut off sandbars and rock shelves), and park above the debris line — the wet sand and stranded seaweed that show where the last high water reached. Check your local page for the exact times, arrive early, and leave yourself an exit that doesn't depend on the water behaving.
Sources
- NOAA Ocean Service: What is a king tide?
- NOAA Tides & Currents (CO-OPS) — perigean spring tide dates from predictions
- NASA Sea Level — the long-term context king tides preview