Simple Tides / Guides / Full Moon Tides

Full Moon Tides: Why the Biggest Tides Follow the Moon

If you've noticed unusually high highs and low lows around a full moon, that's not a coincidence — it's one of the most reliable patterns in tide prediction.

The short version

Around both the full moon and the new moon, the sun, earth, and moon line up (a configuration called syzygy). The sun's gravitational pull adds to the moon's instead of partially canceling it out, which produces a spring tide: a larger-than-average tidal range, with higher highs and lower lows than the days around it.

What to actually expect

Expect the tide chart for the days around a full moon to show a bigger swing between high and low than usual, and expect the water to move a bit faster and the currents to run a bit stronger in between. None of this is dramatic on a day-to-day basis, but it's enough to matter for planning.

Who this matters most for

Anglers — more water movement is one of the inputs behind the Smart Bite Score, alongside the solunar timing tied to the same full moon.
Clammers and tide-poolers — a bigger low tide exposes more of the flats or rocks than usual — see our clamming guide and tide pooling guide.
Coastal residents — the higher high can flirt with minor flooding in low-lying areas, especially if it coincides with wind or rain. When a full-moon spring tide is also near the moon's closest approach to earth, it's often what people call a king tide.