In surfing, what does a wave’s period measure?

In surfing, a wave’s period measures the time between successive wave crests passing a fixed point.

Wave period is usually given in seconds. A longer-period swell has more time between wave sets and generally carries energy from farther away, often producing stronger and more organized waves when it reaches a coastline.

Wave height and wave period describe different properties. Height measures the vertical size of a wave, while period measures the timing between crests. A relatively modest swell with a long period can produce powerful surf because its energy reaches the seafloor and begins interacting with coastal contours.

Forecasts commonly list swell direction, height, and period together. Surfers use all three to judge how a distant storm or weather system may translate into conditions at a particular break.