How to Read a Surf Forecast

Whether you surf regularly or are just starting out, understanding a surf forecast is essential to accurately predict when and where the best conditions will occur.

At first glance, surf reports may seem complex—numbers, arrows, acronyms... However, by identifying and understanding the key elements, you’ll gain a significant advantage when choosing the best time for your next session.

In this guide, we explain the four fundamental factors that determine wave quality: swell, period, wind, and tide. Learning to interpret this data will allow you to plan your sessions more safely and efficiently.

In this guide, we explain the four fundamental factors that determine wave quality: swell, period, wind, and tide. Learning to interpret this data will allow you to plan your sessions more safely and efficiently.

1. The Swell: The Raw Material of the Waves

The swell is generated by storms in the open ocean and can travel thousands of kilometers before reaching the coast. In surf forecasts, you’ll mainly find two pieces of data:

• Swell height: Indicated in meters (or feet), it shows the wave size in open water. It's important to understand that a higher swell height doesn’t always mean better waves, as other factors like period and swell direction also influence wave quality.
• Swell direction: Shown with arrows or cardinal points (N, S, E, W), this tells you where the swell is coming from. Each beach works best with specific directions. For example, if your spot faces north, a north or northwest swell will be more effective than one from the south.

It's also common to see several types of swell in a single forecast: the primary swell is the most relevant, while secondary swells may have a minor influence on overall conditions.

2. Swell Period: Energy and Order

The period is measured in seconds and indicates the time between two consecutive waves. It’s one of the most important factors in determining wave quality:

• Less than 8 seconds: Choppy sea, weak and closely spaced waves.
• Between 8 and 11 seconds: Good conditions for fun sessions, with more defined waves.
• More than 12 seconds: Long-period swell (groundswell), powerful, well-formed, and spaced-out waves.

For example, a 1-meter swell with a 12-second period may offer better waves than a 1.5-meter swell with a 6-second period.

3. Wind: Sculpting the Wave’s Shape

Wind can either improve or completely ruin a session. It’s analyzed according to its direction and speed:

• Offshore (from land to sea): Ideal. It grooms the wave, hollows it out, and improves its shape.
• Onshore (from sea to land): Creates choppy water, foam, and disorganized waves.
• Cross-shore (sideways): May negatively affect the waves, though not as much as onshore.
• Glassy (no wind): Clean and optimal conditions.

Wind strength, measured in km/h or knots, is also key. A light offshore breeze is perfect; if it’s too strong, it can make paddling difficult. Conversely, a light onshore wind may be tolerable, but if it increases, it will ruin the session.

4. Tide: The Ocean’s Rhythm

The tide directly affects how and when waves break at each beach. You need to consider whether it’s high tide (high water) or low tide, and whether it’s rising or falling:

• High tide: At sandy beaches, waves tend to break softer and slower. On reef breaks, it may be the best time to surf.
• Low tide: Produces faster, hollower, and more powerful waves, both on sandbars and reef breaks.
• Transitions (rising or falling): In many spots, the best wave quality occurs during these changes.

Every beach is unique. Knowing how it reacts to different tides is one of the keys to surfing in the best possible conditions.

Practical Example: How to Interpret a Forecast

Let’s say you have the following forecast for tomorrow at 11:00 AM at a beach facing northwest:

• Swell: 1.5 m, 10 s, WNW (West-Northwest)
• Wind: 5 km/h, SE (Southeast)
• Tide: Rising, between low and high tide

Interpretation

• Swell: Good size and acceptable period. The WNW direction is perfect for a northwest-facing beach.
• Wind: Light and from the southeast, so it’s offshore. Excellent.
• Tide: Rising, which can improve wave shape at many sandy spots.

Conclusion

Everything points to a quality session. If the forecast holds, it’ll be a great day for surfing.

Final Recommendation: Practice Observation

Although surf forecasts are a valuable tool, nothing replaces experience. Observe how your favorite beaches respond to different combinations of swell, wind, and tide. Over time, you’ll develop your own judgment and know exactly when it’s the perfect moment to hit the water.

Do you want to improve your skills, better understand your local spot, or choose the best equipment for each condition? At Oceanside, as a surf school, we offer personalised advice and courses designed to help you progress safely and steadily—because knowing the ocean is also part of surfing.