What Makes a Tide a 'King Tide'?
The term 'king tide' is not a scientific one — it's a popular expression originating in Australia and New Zealand to describe an exceptionally high tide. In technical terms, king tides occur during a perigean spring tide: when three conditions align simultaneously.
First, the Moon is at perigee — its closest point to Earth in its elliptical orbit. The Moon's distance from Earth varies by about 50,000 km over each 27.3-day orbit, and at perigee it is roughly 14% closer than at apogee (its furthest point). This proximity amplifies its gravitational pull significantly.
Second, it is a spring tide — the Moon and Sun are aligned (new moon or full moon), so their gravitational forces combine rather than partially cancel.
Third, Earth is near perihelion — its closest point to the Sun in its annual orbit, which occurs around early January each year. This adds a small additional boost.
When all three coincide, the result is the highest predicted tides of the year.
How Much Higher Are King Tides?
The difference depends on your location's baseline tidal range. In areas with moderate tides, a king tide might be 20–30 cm (8–12 inches) above the average high tide — enough to cause nuisance flooding in low-lying coastal areas. In locations with already large tidal ranges, the absolute water level during a king tide can be extraordinary.
For coastal communities, even 20–30 cm of extra water can overtop sea walls, flood stormwater drains, and inundate roads and basements that are normally dry. This is why scientists and planners use king tides as a practical demonstration of what regular high tides may look like in future decades as sea levels rise.
King Tides and Coastal Flooding
King tides can cause what is called 'sunny day flooding' or 'nuisance flooding' — seawater backing up through storm drains, pooling in parking lots, and washing over low seawalls, all with no storm or rain in sight.
The flooding risk increases significantly when a king tide coincides with: - Onshore winds pushing water toward the coast - Storm surge from a distant weather system - High river discharge at estuaries - Low atmospheric pressure (each 1 hPa drop raises sea level by ~1 cm)
In cities like Miami, Sydney, Honolulu, and many low-lying Pacific Island communities, king tides already produce regular flooding events several times per year. As sea levels rise, what is currently a 'king tide' event will eventually become a normal high tide.
When Do King Tides Occur?
King tides are predictable because they are driven by known astronomical cycles. They tend to cluster around two times of year:
November–January: When Earth is near perihelion (closest to Sun, around January 3–5) and a new or full moon occurs, the conditions for a king tide are optimal. The highest king tides of the Northern Hemisphere year often fall in this window.
June–July: A secondary king tide season occurs around aphelion for Southern Hemisphere locations — though these tend to be slightly less extreme than the January peaks.
Within each month, king tides align with new and full moons when the Moon is also near perigee. You can identify upcoming king tide dates by looking at the 10-day tide forecast for your local station and noting which days show the highest predicted high water levels.
How to Find King Tide Dates for Your Location
To identify king tide dates at your local station:
1. Check the monthly tide predictions and look for the highest predicted high water levels — these are your king tide candidates.
2. Pay attention to dates when a new moon or full moon coincides with the Moon being at or near perigee. Moon phase calendars and astronomical apps can show perigee dates.
3. Cross-reference with local weather forecasts closer to the date — storm surge can add to predicted heights.
On TideTimes Global, each station's 10-day forecast displays the predicted water height for every high tide. The days with the tallest predicted highs are your upcoming king tide events.