How it works

What each colour means

• Green

  A good time for your level and for what you are after. Manageable waves, a clean sea and helpful wind.

• Amber

  You can go in, with caveats. Something is off: small surf, a demanding sea, so-so wind. We tell you what.

• Red for safety

  Stay out. Too much size or power for your level, strong gusts, or wind that carries you out to sea.

• Red for poor surf

  No particular danger, but not worth it: a choppy sea or no rideable waves.

What we look at

Seven things, each with its weight in the score from 0 to 100.

• Size20 %

  Wave height against what you and your board can handle.

• Period20 %

  Seconds between waves. More period means more power and longer rides.

• Wind20 %

  Strength, gusts and direction relative to the beach: offshore cleans the sea up, onshore chops it.

• Swell direction15 %

  Where the swell comes from and whether that beach picks it up well.

• Energy10 %

  Wave power, adding groundswell and wind sea together.

• Tide10 %

  Whether it is rising, falling or slack.

• Trend5 %

  Whether the swell is building or dropping fast over the next three hours.

It is not an average

Some things overrule the score, however good it looks:

• Too much sea for your level: red for safety.
• Very strong gusts: red for safety.
• Strong offshore wind, which can carry you out to sea: red for safety.
• A long-period secondary groundswell: it raises the difficulty, because the sets arrive with more power than the report suggests.
• If size, period, direction or wind clearly fall short, there is no green even if everything else is perfect.

It is worked out for you

Your level

Sets the ceiling: how much sea is too much and what wind becomes dangerous. Nothing else can raise that ceiling.

Your board

Shifts the usable range: a longboard works in smaller waves; a foamie makes little of a big swell.

Your goal

Decides what you want within that range. If you want manoeuvres and it is half a metre and weak, it drops to amber. It never turns a demanding day green.

Same sea, two answers

1.4 m waves, a 10 s period and a light offshore wind:

• Beginner

  Stay out today · red for safety

• Intermediate

  Yes, go for it · green

Where the data comes from

• Waves, wind and sea level come from the Open-Meteo models. They are refreshed every 3 hours.
• Beaches and the coastline come from OpenStreetMap. We use the coastline to work out which way each beach faces.

What it cannot know

• It is a model, not a measurement: nobody is measuring the waves at your beach.
• The figures are for open water, a few kilometres out. It can break differently at the shore.
• The orientation of almost every beach is worked out from the map and can be wrong. Each beach page has a map with an arrow: if it does not point out to sea, tell us.
• The tide is an estimate, with a margin of about 45 minutes.
• It cannot see currents, sandbanks, rocks or how crowded the water is.

How far to trust it

High

We have all the data and it has been checked.

Medium

Some data is missing or estimated. This is the usual case.

Low

Several things are missing, or the forecast contradicts itself from hour to hour.