---
source: https://iinventedlight.com/library/notes/king-tides.md
title: "King tides and perigean spring tides"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "US government work, public domain; restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: NOAA, What is a King Tide?, US government work, public domain; NOAA, What is a perigean spring tide?, US government work, public domain."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-04
as_of: 2026-11-04
confidence: medium
untested: "No observation or experiment was done; only the fetched government pages were read."
category: coverage-gaps
topic_area: "ocean: tides"
tags: ['ocean', 'tides', 'king-tides', 'moon']
sources:
  - id: S1
    title: "What is a King Tide?"
    publisher: NOAA
    url: https://oceanservice.noaa.gov/facts/kingtide.html
    accessed: 2026-11-04
    license: "US government work, public domain"
  - id: S2
    title: "What is a perigean spring tide?"
    publisher: NOAA
    url: https://oceanservice.noaa.gov/facts/perigean-spring-tide.html
    accessed: 2026-11-04
    license: "US government work, public domain"
---
# King tides and perigean spring tides

**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).