What Is Wave Period. And Why It Really Matters for Surfers

What is wave period?

The wave period is the time (in seconds) between two consecutive wave crests passing a fixed point. The longer the period, the more energy a wave carries. It’s one of the most important elements of a surf forecast, yet often overlooked by beginners.

Short vs Long: What’s the Difference?

Short period (5–7s): local wind swells – short, choppy, and weak
Long period (10–20s): ocean groundswells – clean, powerful, and organized

Longer Period = Greater Reach

Longer-period swells travel faster and maintain more energy. They can bend (refract) around headlands, islands, or harbors, hitting spots that short-period waves can’t reach. This opens up protected corners and hidden gems. Especially important on coasts with variable wind or swell exposure.

Real-World examples

Portugal (Algarve)

✅ A 2m NW swell with a 14s period will wrap around Cape St. Vincent in the Algarve and produce clean waves at
Zavial and Praia da Luz
❌ That same swell with just 9–10s period won’t make it through – the south coast will likely remain flat.
Lesson: in southern Portugal, swell period makes or breaks your session.

Brittany (France)

Brittany is incredibly diverse, with beaches and reefs facing multiple directions.
✅ With a strong SW swell at 14s+: check the northern-facing points around Brest and Cap Sizun
✅ With a powerful NW swell and long period: head to southern Finistère, where spots south of La Torche come alive
Brittany’s unique shape means swell period helps unlock dozens of options depending on direction and exposure.

Why It Matters for Forecasting

Wave height alone doesn’t tell the full story. Combine height + period to estimate total swell energy (usually expressed in kilojoules). The longer the period, the more powerful (and potentially rideable) the waves.

Recommended forecast tools:
• Surfline – shows individual swell lines and energy levels
• Windguru – includes kilojoule values per swell

➕ Want to learn how to read Windguru like a pro?
Check this guide.

Summary

• Wave period = time between wave peaks, measured in seconds
• Long-period swells carry more energy and travel further
• They can wrap around corners and reach protected surf spots
• Portugal’s south coast and Brittany’s variable coastline are perfect examples
• Always check both wave height and period for the full picture

TL;DR

• Short period (5–7s): choppy, low-energy wind swell
• Long period (10–20s): clean, powerful groundswells
• Longer periods = waves can bend around land and hit sheltered spots
• In the Algarve, swell only reaches surf spots like Zavial at 13–14s+
• In Brittany, longer-period swells unlock a wider range of surfable locations
• Check both wave height and period when planning your session