King Tides

King Tides are predictable and expected, and are natural and occur regularly, but not everyday.  While King Tides can pose challenges at times, they are easily understood and can be planned for!  

YOU CAN HELP!  A little knowledge goes a long way- prepare by marking King Tides on your calendar or following Tide levels in your favorite app.  

Follow forecasted tides in the City's NEW Tide Eye application, which is also available via the City of Charleston mobile app!

What Does the Tide Height Mean?

The average high tide in Charleston is about 5.5 feet, whereas during a King Tide event the high tide may reach 7 feet or higher (MLLW).  

NOAA’s National Weather Service (NWS) Forecast Office in Charleston has established thresholds for flooding in the Charleston area:

  • Action Stage (6.5 ft. MLLW)
  • Minor Flooding (7.0 ft. MLLW)
  • Moderate Flooding (7.5 ft. MLLW)
  • Major Flooding (8.0 ft. MLLW)

NOAA has also established a threshold for high tide flooding (HTF) in Charleston (7.6 ft. MLLW).  Please note, tide heights vary by location!

Perigean Spring Tide diagram from NOAA

King Tides are especially high tide events when there is alignment of the gravitational pull between the sun and moon.

The term "King Tide" is a non-scientific term and describes Perigean Spring Tides, which are the highest seasonal tides that occur each year. 

These tides occur when the moon is either new or full and is closest to the earth in its monthly orbit. These especially high tides can cause or worsen coastal flooding.

Understanding King Tides

In order to understand Perigean Spring Tides, you first have to know that the gravitational pull of the moon and the sun cause tides. Tides are actually long-period waves that roll around the planet as the ocean is 'pulled' back and forth as the moon and the sun interact with the Earth in their monthly and yearly orbits.

The next thing you need to know is that the moon follows an elliptical path around the Earth in its monthly orbit, and the Earth follows an elliptical path in its yearly orbit around the sun. This means that, at times, the moon and the sun are closer to Earth. At other times, they are farther away.

Gravitational Pull

What happens when the moon and the sun are close to the Earth? You guessed it: the gravitational pull they exert is stronger, resulting in slightly higher tides. While both the moon and the sun influence tides, the moon plays a much larger role because it is so close to the Earth. Its gravitational pull is about twice as strong as that of the sun.

King Tides & Coastal Flooding

Major coastal flooding doesn't always occur whenever there is a Perigean Spring Tide, however these tides may often cause minor coastal flooding. Major coastal flooding typically occurs in response to strong onshore winds and barometric pressure changes from a coastal storm. If a storm strikes during a Perigean Spring Tide, flooding could be significantly worse than it otherwise would have been.

In some instances, Perigean Spring Tides have coincided with a shift in offshore ocean circulation patterns and large scale shifts in wind that have resulted in unexpected coastal flooding. It is expected that occurrences of minor coastal flooding at the times of Perigean Spring Tides will increase even more as sea level rises relative to the land.

SC King Tides Initiative

DHEC issues King Tide notifications to MyCoast members when water levels are predicted to reach 6.6 feet above mean lower low water (MLLW) or higher at the Charleston Harbor Tide Station.

Learn More

Learn more about tides (NOAA NWS).

View activity at the Charleston Harbor Tide Gauge (NOAA NWS).

View tide tables to see predicted high tides and king tides in advance (SC DHEC).

SC King Tides Initiative (SC DHEC)

Watch this video to identify the threats of shallow coastal flooding and indicate ways to prepare communities for it (NOAA)

Tidal Datums - what does MLLW mean (NOAA NWS)


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