← All notes

Answer: King tide is a popular, non-scientific name for exceptionally high tides. They usually happen when a new or full moon lines up closely with the Moon's perigee, its closest point to Earth, which scientists call a perigean spring tide. This happens about 6 to 8 times a year.

Why tides get extra high

Tides are long-period waves pulled around the planet by the Moon and Sun. Their pull is strongest when:

• the Sun, Moon and Earth align (new and full moon, spring tides), and
• the Moon is at perigee, and especially when Earth is also near its closest point to the Sun.

Why they matter

King tides can flood low-lying coastal areas. NOAA notes that the effects of perigean spring tides will grow as sea level rises relative to the land.

Claims

• id: C1 claim: King Tide is a non-scientific term for exceptionally high tides. source: S1 evidence: "is a popular, non-scientific term people often use to describe exceptionally high tides"
• id: C2 claim: Higher than normal tides typically occur during a new or full moon. source: S1 evidence: "Higher than normal tides typically occur during a new or full moon"
• id: C3 claim: Perigean spring tides occur often between 6-8 times a year. source: S2 evidence: "Often between 6-8 times a year, the new or full moon coincides closely in time"
• id: C4 claim: High tides during perigean spring tides can be significantly higher. source: S2 evidence: "High tides during perigean spring tides can be significantly higher than during other times of"

Sources

• [S1] What is a King Tide?. NOAA. https://oceanservice.noaa.gov/facts/kingtide.html . License: US government work, public domain. Accessed 2026-11-04.
• [S2] What is a perigean spring tide?. NOAA. https://oceanservice.noaa.gov/facts/perigean-spring-tide.html . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_38a8pc32,
  author = {{iinventedlight}},
  title = {{King tides and perigean spring tides}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/king-tides/},
  note = {Permanent ID iil:note:38a8pc32. License: CC-BY-4.0.},
}

Markdown

Spotted a mistake? Use the MCP feedback tool or email hello@iinventedlight.com.

For language models and agents: start at /llms.txt. This page in Markdown: /library/notes/king-tides.md.