How to Read a Surf Forecast

Updated 29 September 2026

A surf forecast helps answer three questions. How big the waves are likely to be, how well formed they are likely to be, and when to go. This guide explains how to read those answers on Setform, both for people who are new to surfing and for experienced surfers. No prior knowledge is assumed, and every term is explained the first time it appears.

This guide is general information to help you get started. It is not expert or safety advice. Every surf spot behaves in its own way, and conditions often differ from the general patterns described here.

For how each figure is calculated, see where our data comes from.

Step by step

1. Pick a spot. Setform covers a chosen catalogue of well known surf spots around the world, such as Pipeline and Ericeira. Pick one from the world map on the home page, from the Surf spots menu at the top of a spot page, or by searching by name or region.
2. The page opens on the current time. The header shows the spot’s name, the sea temperature, and the word Now beside the spot’s local time. The wave drawn on screen is built from the forecast figures for that moment.
3. Read the height and the period first. The height sits beside the wave, labelled Primary swell. The period sits in the Conditions card. Height gives an idea of how big the waves may be. Period gives an idea of how powerful and how well organised they may be.
4. Then read the wind. The Conditions card shows the direction the wind comes from, how fast it is forecast to blow, and how strong the gusts are forecast to be. The details say whether that wind is Offshore, Cross-shore or Onshore at the spot.
5. Then check the tide. Markers along the timeline show each forecast high and low tide. The details show whether the water is rising or falling, and the times of the next high and the next low.
6. Open the details. On a computer, select Show details at the foot of the screen. On a phone, drag the panel up. The details hold a chart for each figure and a table of the readings at the chosen time.
7. Look ahead. The timeline along the bottom covers the next three days on a computer, and the next 24 hours on a phone, in the Hourly tab. Move along it to see any hour, and the wave, the header and the Conditions card change to match.

Wave height: how big the waves are

Wave height is usually given as the vertical distance from the lowest point of a wave to its highest point. The height beside the wave, labelled Primary swell, is the height of the main set of waves, explained below under two sets of waves at once. The ruler beside the wave uses the same scale.

Setform shows heights in feet or metres. The ft and m buttons, on the left of the screen below the water line, switch between them. Feet also sets wind speed to miles per hour and the sea temperature to Fahrenheit. Metres sets them to kilometres per hour and Celsius. Your choice is remembered on your device, and account holders can also set it under Measurement units in their account settings.

The height given describes the waves out in open water. It is often different from the height of the waves as they rise close to shore. How a wave stands up depends largely on the shape of the seabed beneath it, and a forecast model does not know any particular seabed in detail.

For beginners: many people learn on small waves, often under about three feet or one metre, and often at a sandy beach. Waves that look small on a forecast can still be powerful, so it helps to read the height together with the period.

Swell 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 gives a general sense of how organised the waves are.

A long period usually means the energy has travelled a long way from the weather that created it. Over that distance, waves tend to sort themselves into more even, well spaced lines, and they often arrive with more power. A short period often means the waves were raised by wind closer to the shore, and they tend to arrive weaker, closer together and rougher.

Two forecasts showing the same height can describe very different conditions. As a general example, three feet at fourteen seconds is often a well formed wave, while three feet at six seconds is often disorganised water.

A longer period generally means more power. At the same height, a wave with a long period tends to break harder and move faster than a wave with a short period. Many experienced surfers look for that power. For a beginner, it can make a small forecast harder and more dangerous than the height suggests.

Setform shows the period as a number of seconds, such as 12.3s, and does not label it good or poor. What counts as a long period varies from one coastline to another, so the judgement is left to you.

The timeline is coloured hour by hour by the period of the main set of waves. Hours under 8 seconds are grey, and the colour changes at 8, 10, 13 and 15 seconds, from shorter to longer. This makes it quick to find the hours with the longest periods.

Two sets of waves at once

The sea often carries more than one set of waves at the same time, raised by different weather, arriving from different angles, with different periods. Setform shows two sets.

They are named Swell and Wind swell. Swell is usually the set that has travelled in from distant weather. Wind swell is usually the set raised by wind closer to the coast. Alongside them is a Combined figure, which describes the sea as a whole rather than either set on its own.

In the details, one of the two sets is tagged (Pri), for primary, and the other (Sec), for secondary. The wave drawn on screen, the Primary swell height, the period in the Conditions card and the swell compass all describe the primary set.

Primary does not mean taller. It means carrying more energy by Setform’s calculation, which depends on the period as well as the height. Setform takes each set’s height, multiplies it by itself, then multiplies the result by that set’s period, and features whichever set produces the larger number. Where our data comes from sets out the arithmetic.

The taller set is therefore not always tagged Pri. A four foot set at five seconds can be tagged Sec beside a three and a half foot set at ten seconds tagged Pri, because ten seconds is more than twice five, and that outweighs the difference in height in the calculation. In cases like this, the set with the longer period often carries the more rideable waves, while the taller set is often short, rough water raised by nearby wind.

Two more points about these figures:

• The Combined height is usually the largest height in the details, because it accounts for the whole sea. It is not the two sets added together. Wave heights combine through the energy the waves carry, so 2 ft of swell and 1 ft of wind swell make a Combined height of roughly 2.2 ft, not 3 ft. The Combined period is an average across all the waves, so it often sits between the periods of the two sets rather than above them. The Combined height is not a direct measure of the waves you are likely to ride, and reading it that way can overstate the conditions.
• When the two sets are close in energy, the tags can swap from one hour to the next. This usually means the sea is mixed, with neither set clearly stronger, and the waves are often less orderly than either figure on its own suggests.

Swell direction: where the waves come from

Direction is the compass point the waves are travelling from. It matters because a spot generally needs waves that can reach it. A spot sheltered by a headland or an island can stay small, or flat, even when waves are large elsewhere, if they arrive from an angle it is not open to.

The swell compass in the Conditions card is a view from above, turned so that the sea is on the left and the land is on the right. The letters N, E, S and W mark the compass points, and the arrow points the way the waves are travelling. Above the compass, the direction is written as the point the waves come from and its angle in degrees, such as WNW 292° for west north west. The details give the same point.

On many spots, a solid blue band runs around the edge of the swell compass. It marks the range of swell directions that surf guides generally agree tend to work at that spot. When the arrow’s tail points into the band, the waves are coming from within that range. The band is a general guide, not a rating. A swell from inside the range can still be too small, too large or spoiled by wind, and a swell from outside it can sometimes still produce good waves. Spots without a widely agreed range show no band. Where our data comes from explains how each range is chosen.

On some spots the band sits over the land side of the compass. Waves there often bend around a headland or point before they reach the shore, so the swell can arrive from a direction the beach itself does not face.

Where two sets of waves are running at once, the compass describes the primary set. The other set’s direction is listed in the details.

Wind: offshore, cross-shore and onshore

Wind affects the surface of the water and how smooth or rough the waves look. Good waves with unsuitable wind can be unpleasant, and modest waves with suitable wind can be very enjoyable.

• Offshore means the wind is blowing from the land out to sea. It often holds the front of the wave up and keeps its surface smooth, and many surfers hope for it.
• Onshore means the wind is blowing from the sea towards the land. It tends to break the surface up, and it is a common reason a promising forecast disappoints.
• Cross-shore means the wind is running along the shore from one side. Its effect usually sits between the other two, and it varies from spot to spot. On a phone it is shortened to Cross.

Strength matters as well as direction. A light offshore wind often improves a wave, while a very strong one can hold the wave up so much that it does not break well. As a rough guide, many surfers find that wind under about 10 miles per hour, or 15 kilometres per hour, leaves the surface fairly smooth, and that stronger wind tends to make it rougher, especially when it is onshore.

The Conditions card shows the average wind speed, followed by the gusts in brackets when they are stronger, such as 9 (22) mph. Gusts are the highest speeds the wind is forecast to reach in short bursts, and the details list them on their own row. A wide gap between the two often means changeable wind, and the water may be rougher than the average speed on its own suggests.

The wind compass works like the swell compass: sea on the left, land on the right, and the arrow pointing the way the wind is blowing. Above it, the wind’s direction is written the same way as the swell’s, such as S 190°. Whether that wind is offshore, cross-shore or onshore is in the Shore row of the details.

Whether a wind counts as offshore depends on which way the spot faces, so this reading is one Setform calculates rather than one the weather data supplies. Where our data comes from sets out how it is worked out.

Tide: why a spot changes through the day

Tide is the regular rise and fall of the sea, caused mainly by the pull of the moon and the sun. Many coasts have two high tides and two low tides a day. As the water becomes deeper or shallower over the rock or sand below, it can change how and where the waves break. Many spots work best at particular stages of the tide, and some may not work well outside them.

Markers along the timeline show each forecast high and low tide, and selecting one moves the timeline to it. In the details, Trend shows whether the water is Rising, Falling or Slack, the time around high or low water when the level changes little. Current shows the level above or below normal, and Next high and Next low give the forecast times of the next turns.

Which stage of the tide suits a particular spot is local knowledge that a forecast cannot supply. People who know the place, or watching it over several visits, are usually the best guide.

Water temperature

The header shows the forecast temperature of the sea surface, such as 63°F water. It follows the timeline, so a later hour shows the figure for that hour. It is shown in Fahrenheit when heights are in feet, and in Celsius when heights are in metres.

It can be used as a rough guide to what to wear in the water. The figure describes open water near the coast, and the water close to shore can differ by several degrees, often colder, so check local advice as well.

Where the forecast applies

The Location section describes the place rather than the conditions. On a computer it sits at the end of the details. On a phone it has its own Location tab.

• The overview, headed About and the spot’s name, gives a general description of where the spot is and what it is known for.
• Surf spot is a small map of the spot seen from above, with the sea on the left. Forecast heading is Setform’s estimate of the direction the spot faces towards the open sea, which Setform uses to work out whether the wind is offshore. Reference axis is the dashed line at a right angle to it, and at most spots it roughly follows the line of the coast.
• Open-Meteo sea forecast cell is the patch of sea the wave figures describe, with its size and its distance and direction from the spot. At some spots it lies several kilometres out to sea. Where the forecast is measured explains why.
• Open-Meteo wind forecast point is the place the wind reading comes from, with its distance and direction from the spot. Measured over says whether that point is over land or open water.
• Suggested spots lists the three nearest other spots in the catalogue.

Putting it together

There is rarely one perfect figure. Good conditions usually come from a combination, and what suits you depends on your experience and on the spot.

Many beginners look for something like this:

• Small waves, often under about three feet or one metre.
• A moderate period, so the waves tend to arrive with less power.
• Light wind, or none.
• A sandy beach with lifeguards on duty, or a lesson with a qualified surf school.

Many experienced surfers look for something like this:

• A height that suits the spot and their ability.
• A period long enough that the waves tend to arrive evenly spaced and well formed.
• A swell direction the spot is generally open to.
• Light wind, ideally offshore, with gusts close to the average speed.
• A stage of tide the spot is known to work on.

When these line up, conditions are often favourable. When they do not, one factor is often the cause, and the timeline may show a later hour when it changes. A forecast can only suggest what conditions may be like, so always check them in person before going in.

What a forecast cannot tell you

A forecast is a model of the ocean, not a measurement of it, and it can be wrong. Setform’s forecast covers the next three days. Forecasts are generally more reliable a day or two ahead than further out. 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.

Where the figures come from

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

Questions about this guide? Email [email protected].