How Often Do Spring Tides Occur? The Twice-Monthly Cycle

Spring tides occur roughly twice a month, once at each new moon and once at each full moon, so they arrive about every 14 to 15 days. A spring tide is a tide with the largest difference between high and low water, caused by the Sun and Moon pulling in line with Earth. The name has nothing to do with the season — it comes from the idea of the tide “springing” or rising up. So if you are asking how often do spring tides occur, the short answer is two times per lunar month, spaced roughly two weeks apart.

What Causes Spring Tides

A spring tide happens when the Sun, Moon, and Earth fall into a straight line. At that moment, the gravitational pull of the Sun and the Moon combine on the same axis, and their effects reinforce each other rather than partly cancel out.

That alignment occurs at two points in the lunar cycle: the new moon, when the Moon sits between Earth and the Sun, and the full moon, when Earth sits between the Sun and the Moon. During both phases the three bodies are nearly aligned, so the tidal bulge raised by the Moon is stretched further by the Sun.

Why the Alignment Matters

The Sun’s pull on the oceans is weaker than the Moon’s — roughly 46 percent as strong, according to NOAA National Ocean Service — but it is far from trivial. When the two pulls line up, the high tides run higher and the low tides run lower. That enlarged range between high and low water is the defining mark of a spring tide.

One common misunderstanding is worth clearing up: spring tides are not unique to spring. They happen all year round, in every season, because they depend on the Moon’s phase rather than the calendar month.

How Often They Occur

Spring tides appear about twice per month — one per new moon and one per full moon — which works out to roughly every 14 to 15 days. The National Geographic Society notes that the Sun and Moon align in this way about twice a month, producing the extra-large tidal range each time (National Geographic Society).

This “twice-monthly” rhythm is the core fact to remember. It holds steady month after month because the Moon keeps cycling through its phases on a dependable schedule.

A Quick Worked Example

Imagine a coastal town where an ordinary high tide peaks around 3.0 meters. During a spring tide, the combined pull of the Sun and Moon might push that high tide noticeably higher and pull the low tide lower, widening the gap. Two weeks later, when the Moon reaches the opposite phase, the same thing happens again. That gives the town two extra-large tidal ranges in a single month.

The exact heights vary by location — shoreline shape, water depth, and local geography all matter — but the twice-monthly timing is universal.

Monthly Timing Pattern

Spring tides do not land exactly on the day of a new or full moon. Instead, they typically show up about one to two days afterward, because the ocean does not respond to the Sun and Moon’s pull instantly.

The underlying clock is the lunar cycle, which runs about 29.5 days from one new moon to the next. This is called the synodic month, and it is the period over which the Moon completes its full set of phases.

How the Cycle Unfolds

Here is the pattern in sequence:

• New moon arrives, and a spring tide follows a day or two later.
• About seven days pass; the Moon reaches first quarter, and a neap tide sets in.
• Full moon arrives, and another spring tide follows within a day or two.
• About seven days pass; the Moon reaches last quarter, and another neap tide arrives.
• The Moon returns to new, and the cycle repeats.

Because the lunar cycle is slightly longer than the average calendar month, the days on which spring tides fall drift forward a little each month. Over time they work their way through the calendar, which is why the alignment does not stay locked to one date.

Spring vs Neap Tides

Between each pair of spring tides come the neap tides — the tides with the smallest difference between high and low water. They arrive when the Sun and Moon pull at right angles to each other, during the first and last quarter phases of the Moon.

At those points, the Sun’s pull partly offsets the Moon’s instead of boosting it, so high tides come in lower and low tides do not retreat as far. The result is a gentler, smaller tidal range.

Seeing the Full Cycle

Put together, a single lunar month contains two spring tides and two neap tides, alternating roughly every seven days. The cycle runs spring, neap, spring, neap — a steady rhythm driven by the Moon’s phases and its shifting angle to the Sun.

For anyone planning around tides — fishing, surfing, boating, or simply visiting a beach — this alternation is the practical takeaway. If you can identify the upcoming new or full moon, you already know that the biggest tidal swings are only a day or two behind it, and that calmer neap ranges sit about a week on either side.

Key Takeaways

• Spring tides occur twice a month — at each new moon and each full moon — roughly every 14 to 15 days.
• They form when the Sun, Moon, and Earth align, letting the two gravitational pulls reinforce each other.
• The full-cycle clock is the lunar month of about 29.5 days; spring tides usually trail the new or full moon by one to two days.
• Neap tides fill the gaps, arriving about a week after each spring tide during the Moon’s quarter phases.
• Spring tides are not seasonal — the term refers to the tide “springing” higher, not to the spring season.