How to Read a Surf Forecast

Updated 18 August 2026

A surf forecast answers three questions. How big will the waves be, how well formed will they be, and when should you go. This page explains how to read those answers on Setform. No prior knowledge is assumed, and every term is explained the first time it appears.

For the detail of how each figure is calculated, see Our Data.

Your first five minutes

This is the short version. Everything after it is the detail behind each step.

Pick a spot. Setform covers a chosen catalogue of well known surf spots around the world. Pick one from the world map on the home page, from the location menu, or by typing a name into the search field.
You arrive at right now. A spot always opens on the current hour. The wave drawn on screen is built from that hour's figures, so you are looking at the forecast itself rather than a picture of the sea.
Read the height and the period first. Height tells you how big the waves are. Period tells you how well formed they will be.
Then read the wind. The Conditions card shows Offshore, Cross-shore or Onshore. Offshore is the one to hope for.
Then check the tide. It shows whether the water is rising or falling, and the time of the next high and the next low.
Open the details. Expanding the panel at the foot of the screen breaks every figure out into its own chart and table, hour by hour.
Look ahead. The timeline along the bottom covers the whole forecast window. Move along it to see any hour, and the wave redraws itself as you go.

One combination is worth remembering. A long period with a light offshore wind is a good sign at almost any spot.

Height: how big the waves are

Height is the vertical distance from the lowest point of a wave to its highest point. Setform shows it in feet or metres. You can change the unit with the toggle near the top of the screen, and if you have an account you can set the unit you prefer permanently.

The height given is the height of the waves out in open water. It is not the height of the wave as it rises in front of you close to shore. How a wave stands up depends on the shape of the seabed beneath it, and a forecast model does not know any particular seabed in detail.

Period: the seconds between waves

Period is the number of seconds between one wave passing a fixed point and the next one passing it. It describes how well organised the waves are.

A long period means the energy has travelled a long way from the storm that created it. Over that distance the waves sort themselves into even, well spaced lines, and they arrive with power. A short period means the waves were raised by wind close to the shore. They arrive weak, bunched together and rough.

Two forecasts showing the same height can describe completely different days. Three feet at fourteen seconds is a well formed wave. Three feet at six seconds is disorganised water.

Setform shows the period as a plain number of seconds and does not label it good or poor. The line between well formed and rough moves from one coastline to another. A period that counts as long in one part of the world is unremarkable in another, so the judgement is left to you.

The coloured bar under the timeline shades every hour by its period, which makes it quick to find the stretch of hours when the best organised waves arrive.

Direction: where the waves come from

Direction is the compass bearing the waves are travelling from. It matters because a spot only works when the waves can reach it. A spot tucked behind a headland or an island can stay flat on a big day if the waves are arriving from the wrong angle.

The compass discs on Setform are drawn from the point of view of somebody standing on the beach and looking out to sea. The water is the left half of the disc and the land is the right half. The written bearing tells you where the waves are coming from. The arrow points the way they are travelling.

Open water usually carries more than one set of waves at once, and Setform features whichever set is carrying the most energy. Our Data sets out how that choice is made and where to see the set that was not featured.

Wind: offshore, cross-shore and onshore

Wind shapes the surface of the water and decides how smooth or rough the waves look. Good waves with the wrong wind are unpleasant. Modest waves with the right wind can be excellent.

Offshore means the wind is blowing from the land out to sea, into the back of the wave. It holds the front of the wave up and keeps its surface smooth. This is the one to hope for.
Onshore means the wind is blowing from the sea towards the land. It breaks the surface up, and it is the usual reason a promising forecast disappoints.
Cross-shore means the wind is running along the shore from one side. It sits between the other two, and it tends to make the waves less predictable rather than simply worse.

Strength matters as much as direction. A light offshore wind improves a wave. A very strong one can hold the wave up so much that it does not break properly at all.

Setform shows the gust speed beside the average speed. The gust figure is the peak the wind is expected to reach, not the speed it holds. A wide gap between the two means an unsettled day, and the water will be rougher than the average speed on its own suggests.

Whether a wind counts as offshore depends on which way the shore faces, so this reading is one Setform calculates rather than one the weather data supplies. Our Data sets out how it is worked out.

Tide: why a spot changes through the day

Tide is the slow rise and fall of the sea, caused by the pull of the moon and the sun. As the water becomes deeper or shallower over the rock or sand below, it changes how and where the waves break. Most spots work best at a particular stage of the tide, and some do not work at all outside it.

Setform shows the level right now, whether the water is rising or falling, and the time of the next high and the next low. Which stage a particular spot needs is local knowledge, and it is the one part of this that a forecast cannot supply. Ask somebody who knows the place, or watch it across a few visits.

Putting it together

A good day is rarely one perfect figure. It is a combination, and it usually looks like this.

A height you are comfortable with. For a beginner that means small.
A period long enough that the waves arrive evenly spaced and well formed.
A wave direction the spot is open to.
Light wind, ideally offshore, with gusts close to the average speed.
A stage of tide the spot works on.

When those line up, the forecast is telling you to go. When they do not, it is usually one of them spoiling the rest, and the timeline will often show you an hour later in the day when that one has passed.

What a forecast cannot tell you

A forecast is a model of the ocean, not a measurement of it. It is at its most reliable a day or two ahead, and less reliable after that. It describes open water rather than the exact piece of coast you are standing on.

It carries no knowledge of rip currents, rocks, sea life, water quality, crowds, closed beaches, local rules, or how the sand shifted after the last storm. Those things come from people who know the place, from lifeguards, and from local authorities.

Surfing is dangerous and conditions change quickly. Never rely on this or any forecast on its own. Always judge the conditions in person, respect local warnings and lifeguards, know your own limits, and do not go out alone if you are unsure.

Where the figures come from

Setform does not measure the sea. It reads open weather data and presents it. Our Data names the source, sets out the arithmetic behind every figure, and describes what the data cannot do.

Is something here unclear, or is there a term you expected to find? Email [email protected].