Swell period is the time (in seconds) between successive swell waves passing a fixed point. It indicates how much energy a swell carries: long-period swell (12+ seconds) is generated by distant storms, carries large amounts of organised energy, produces powerful clean waves and wraps into more surf spots. Short-period swell (under 8 seconds) is locally wind-generated, weak and choppy. Experienced surfers check period before height — a 1.5m swell at 14 seconds produces far better, more powerful waves than 1.5m at 6 seconds. Period is one of the most misunderstood but important surf-forecast metrics.
Key points
- Seconds between swell lines
- Long period (12s+) = powerful, organised waves
- Short period (under 8s) = weak, choppy
- Often matters more than swell height
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