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What is a king tide?

King tide: an abnormally high spring tide | Photo: Shutterstock

King tides are extremely high spring tides that occur when the gravitational forces of the Moon and Sun align with Earth in a way that amplifies their effects on ocean water levels.

While the term "king tide" isn't scientific, it has become widely used to describe these exceptional tidal events.

These phenomena result from a combination of factors, including:

  • Spring Tides: These occur during new and full moons when the gravitational pull of the Moon and Sun are aligned, leading to higher-than-normal tidal ranges;
  • Perigee: The Moon's orbit around Earth is elliptical, meaning its distance from Earth varies. Perigee is when the Moon is closest to Earth, intensifying its gravitational influence;
  • Perihelion: Similarly, Earth's orbit around the Sun is elliptical, and perihelion is when Earth is closest to the Sun, usually in early January, enhancing tidal effects;

When spring tides coincide with the Moon's perigee and Earth's perihelion, the resulting tides are the highest of the year - what we call king tides.

So, technically, a king tide is indeed a spring tide.

When Do King Tides Occur?

King tides typically happen once, twice, three, or four times a year and can be predicted based on the orbits of the Earth, the Moon, and the Sun.

Because these orbits follow consistent cycles, scientists can forecast these higher-than-usual tides years in advance.

They usually occur in specific seasons depending on the geographic location, such as around January when Earth is closest to the Sun.

King tides: they can occur two or three times a year and result in flooding | Photo: Shutterstock

What Are Their Impacts?

Extreme tidal phenomena have impacts on coastal regions, but they can also leave hints about the future.

Here's what an extraordinarily high tide brings:

  1. High Water Levels: King tides bring unusually high water levels, often higher than the typical high tide. Consequently, coastal communities could experience flooding in low-lying areas, even on sunny days and without rain, which may disrupt local infrastructure, roads, and homes;
  2. Flooding and Infrastructure Risks: They reveal areas that are most vulnerable to flooding, providing valuable insights for urban planning, coastal management, and infrastructure development;
  3. A Glimpse into the Future: King tides offer a preview of what everyday high tides could look like in the future due to sea level rise. As global water levels increase, they may become a regular inconvenience;

It is also important to stress that the height and impact of these abnormally high tides can be boosted by other weather events like intense rainfall, storm-generated swells, El Niño, and strong winds.

Are King Tides Predictable?

The predictability of king tides comes from their dependence on celestial mechanics. There is no way around it.

We do know that the movements of the Earth, the Moon, and the Sun follow regular patterns. For instance:

  • The Moon's elliptical orbit around Earth takes about 29 days to complete;
  • The alignment of the Earth-Moon-Sun system occurs approximately every two weeks during the lunar cycle;
  • Earth's closest approach to the Sun, perihelion, happens annually;

These patterns allow scientists to forecast super-high tides with precision, making them regular and expected events.

In the United States, you can check the heights of the king tides on the National Oceanic and Atmospheric Administration's (NOAA) tide tables.

While they can reach 6.5 feet (2 meters) in many regions, it is possible to observe 16.5-foot (5-meter) water height in, for instance, Puget Sound, Washington.

Why Is Monitoring Important?

There are several reasons why observing king tides, measuring, and taking notes of their impacts is very important.

Here are a few:

  • Raising Awareness: They provide a real-time demonstration of the effects of higher water levels, helping communities understand the long-term impacts of climate change;
  • Planning: Data collected during king tides can identify flood-prone areas and inform strategies for mitigating risks to infrastructure, housing, and ecosystems;
  • Community Engagement: These tidal events often attract attention, serving as opportunities to educate the public about coastal resilience and environmental stewardship;


Words by Luís MP | Founder of SurferToday.com



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