Spring tides are long-period waves that roll around the planet as the ocean is "pulled" back and forth by the gravitational pull of the moon and the sun as these bodies interact with the Earth in their monthly and yearly orbits. During full or new moons, which occur when the Earth, sun, and moon are nearly in alignment, average tidal ranges are slightly larger. This occurs twice each month. The moon appears new (dark) when it is directly between the Earth and the sun. The moon appears full when the Earth is between the moon and the sun. In both cases, the gravitational pull of the sun is "added" to the gravitational pull of the moon on Earth, causing the oceans to bulge a bit more than usual. This means that high tides are a little higher and low tides are a little lower than average. These are called spring tides, a common historical term that has nothing to do with the season of spring. Rather, the term is derived from the concept of the tide "springing forth." Spring tides occur twice each lunar month all year long, without regard to the season.

A neap tide, on the other hand, refers to a period of moderate tides when the sun and moon are at right angles to each other. Seven days after a spring tide, the sun and moon are at right angles to each other. When this happens, the bulge of the ocean caused by the sun partially cancels out the bulge of the ocean caused by the moon. This produces moderate tides known as neap tides, meaning that high tides are a little lower and low tides are a little higher than average. Neap tides occur during the first and third quarter moon, when the moon appears.

A perigean spring tide is a tide that occurs three or four times per year when a perigee (the point nearest Earth reached by the Moon during its 27.3-day elliptic orbit) coincides with a spring tide. This has a slight but measurable impact on the spring tide, usually adding no more than a couple of inches. Typically between 6-8 times each year, the new or full moon coincides closely in time with the perigee of the moon — the point when the moon is closest to the Earth. These occurrences are often called perigean spring tides. The difference between perigean spring tides and spring tides that occur closer to the moon’s apogee are location dependent and significantly influenced by tidal range, but can be quite large.