How do you read a surf forecast?

1. Swell height

This is the most-watched figure, given in metres or feet (1 foot ≈ 0.30 m). Careful: it indicates the size of the swell out at sea, not necessarily the size of the waves at the shore. Depending on the sea floor, the spot's orientation and above all the period, a 1 m swell can produce noticeably smaller or bigger waves at the beach.

A beginner aims for small and clean; an experienced surfer looks for more volume. But height alone tells you nothing: it's always read together with the period. Some services also distinguish the "primary" swell (the main one, the one that has travelled) from secondary swells and local chop — it's the long-period swell that makes the wave.

2. Period: the most important factor

The period (in seconds) is the interval between two successive waves. It's the parameter beginners most underestimate, and the most decisive. A long period comes from a swell formed far away by a big storm: it has travelled, organised itself and arrives powerful, regular and clean. A short period comes from a nearby local wind: a short, messy sea, chop rather than real waves.

For the same height, a long period gives much bigger and more consistent waves than a short one. That's why 1 m at 14 s can be more serious than 1.5 m at 7 s.

3. The direction of the swell and the spot

The swell arrives along a bearing (N, NW, W, SW, S…). Each spot is only exposed to certain directions because of its orientation and the headlands, capes or islands that shelter it. A west swell can light up a west-facing beach and leave the neighbouring south-facing cove almost flat.

• Well-oriented swell: it enters the bay fully, the wave has size and shape.
• Poorly oriented swell: part of the energy is blocked or passes by, the spot stays small or closes out.
• The spot's "window": knowing the directions that work (and those that don't) saves you a wasted trip.

This is where local knowledge counts: the same swell day can be excellent in one place and useless 10 km away.

4. The wind: offshore, onshore, cross-shore

The wind determines the quality of the session, regardless of the size of the waves.

• Offshore (from land towards the sea): it holds the wave up, makes it hollow and smooths the surface. It's the wind you want, especially light; too strong, it can make the take-off harder.
• Onshore (from the sea towards land): it disorganises and chops up the surface, waves turn soft and close out early.
• Cross-shore (from the side, along the beach): in between, often manageable as long as it stays light.

Remember the hierarchy: a strong wind always degrades, whatever its direction; light offshore is ideal; no wind (a "glassy" sea, smooth as a mirror) is perfect too. Look at both the direction and the strength of the wind (in km/h or knots; 1 knot ≈ 1.85 km/h).

5. The tide: the right level at the right moment

Every spot has a tide that suits it: low, mid incoming, mid outgoing, or high. The same place can be perfect at mid-tide and unsurfable at low tide (waves that close out, turn soft or stop breaking). On coasts with a large tidal range like the French Atlantic, the effect is major.

A tide forecast gives the times of high and low water and the coefficient (the day's range). Spot the window where the level matches the spot, then time your session around it. In practice, you cross-check "the spot's ideal tide" with "the time the wind is lightest" — often early in the morning.

6. Putting the five together + glossary

Reading a forecast is about the overall picture, not looking at a single number. A good session brings together: swell present and well-oriented + long period + light or offshore wind + a tide that suits the spot + a wave size matched to yours. If just one of these is badly off (strong onshore wind, wrong tide), the session suffers for it.

Always compare several sources and, if you can, the forecast against the actual conditions observed on site: models sometimes get it wrong. BeachFinder shows the swell, period, wind and tide for the spot, rated by the community, which helps you check the forecast against what's really happening on the ground.