Why is it important to read a surf forecast?
Imagine driving an hour to the beach only to find the ocean completely flat. Or worse: giant waves and cross-shore wind making it impossible to surf. Knowing how to read a surf forecast saves you time, money, and frustration, and lets you choose the best day, time, and spot for your session.
A surf forecast is simply a specialized ocean weather prediction. It combines data about swell, wind, tides, and general conditions to give you an idea of what the ocean will look like in the coming hours and days.
In this guide, we'll break down each variable, explain what it means, and teach you how to combine them to make better decisions. You don't need to be a meteorologist — just understand the basics.
1. Wave Height
Wave height is the most visible data point in any forecast and is generally measured in meters. It represents the vertical distance between the lowest point (trough) and the highest point (crest) of the wave in open water.
It's important to understand that the forecast height isn't exactly what you'll see at the beach. How waves break depends on the seabed, beach slope, and swell direction. A 1.5m wave at a reef break can be more powerful than a 2m wave at an open beach break.
General ranges for beginners:
- 0 - 0.5m: Very small. Can be hard to catch waves, but safe for learning.
- 0.5 - 1.0m: Ideal for beginners. Enough waves to practice without being intimidating.
- 1.0 - 1.5m: Good conditions for intermediates. Experienced beginners can give it a try.
- 1.5 - 2.0m: Waves with real power. Recommended for experienced surfers.
- 2.0m+: Demanding conditions. Only for advanced surfers who know the spot.
Tip: If you're just starting out, look for days with 0.5 to 1.0 meter waves and medium period. It's the friendliest combination for learning.
2. Wave Period
The period is the time in seconds between one wave and the next. It's perhaps the most underrated data point for beginners, but one of the most important for experienced surfers.
Why does it matter? Because the period determines the energy and quality of the waves:
- 5-8 seconds: Wind swell (locally generated). Messy, short waves with little power. Not ideal for surfing.
- 9-11 seconds: Medium swell. More organized waves with better shape. Good for most spots.
- 12-15 seconds: Ground swell. Powerful, clean, well-formed waves. Excellent conditions.
- 16+ seconds: Long-traveled swell. Very powerful waves that traveled thousands of kilometers. The best days at most spots.
A simple trick: the longer the period, the more energy. A 1m wave with a 15-second period can be more powerful and surfable than a 1.5m wave with 7 seconds. The period multiplies quality.
In Peru, the best swells usually arrive with 14 to 18 second periods from the south-southwest, generated by storms in Antarctica and the South Pacific.
3. Swell Direction
Swell direction indicates where the waves are coming from, expressed in degrees or cardinal points (N, NNE, S, SSW, etc.). It's crucial because it determines which spots will work and which won't.
Each beach has a specific orientation and receives certain swell angles better:
- South (S) and South-Southwest (SSW/SW) swell: The most common in Peru from April to October. Activates most spots on the central and northern coast: Chicama, Punta Rocas, Pacasmayo, Cerro Azul, Huanchaco.
- West (W) and Northwest (NW/WNW) swell: More frequent in summer. Works well at north-facing spots like Mancora, Lobitos, and Organos.
- North (N/NNW) swell: Less common but activates northern Peru spots in summer.
Practical example: If the forecast says "SSW swell of 1.5m at 14s," you know that Chicama and most spots on the Peruvian coast will have good waves. But if it says "NW swell of 1m at 8s," probably only some northern spots will work.
4. Wind
Wind is the factor that most affects the visual and surfable quality of waves. A perfect wave can be ruined by the wrong wind.
Wind types based on direction relative to the beach:
- Offshore (land to sea): A surfer's best friend. It holds up the wave face, making it cleaner, hollower, and more defined. Mornings in Peru tend to be offshore — that's why surfers wake up early.
- Onshore (sea to land): The enemy. Pushes waves making them messy, foamy, and shapeless. Typically picks up in the afternoons.
- Cross-shore (lateral): Crosswind. Not ideal but surfable if not too strong.
- Glass (no wind): Ideal conditions. The ocean surface is like a mirror and waves maintain their natural shape.
Wind intensity:
- 0-10 km/h: Little to no effect. Excellent conditions.
- 10-20 km/h: Noticeable. If offshore, it improves waves. If onshore, it starts to damage them.
- 20-30 km/h: Strong. Only offshore is desirable. Onshore ruins conditions.
- 30+ km/h: Very strong. Difficult to surf in any direction.
Golden rule: Look for early morning sessions (6-10am), when wind tends to be calm or slightly offshore. In Peru, onshore wind almost always picks up after noon.
5. Tides
Tides are changes in sea level caused by the gravitational pull of the Moon and Sun. Water level rises (high tide) and falls (low tide) approximately every 6 hours.
Tides affect how waves break depending on the bottom type:
- Beach breaks (sandy bottom): Usually work best at low to mid tide, when sandbars are more exposed and waves break with more definition.
- Reef/point breaks (rocky bottom): May need more water (mid to high tide) to be surfable and safe. At very low tide, rocks can be exposed.
In Peru, tides are micro-tides (0.5 to 0.8 meter range), so their effect is less than in other countries. However, at shallow spots like some reef breaks, the difference can be felt.
Tip: If you don't know the spot, ask locals or the surf school about the best tide for surfing there.
6. Wave Energy
Some advanced forecasts display wave energy in kilojoules (kJ). This metric combines height and period into a single number that represents the real power of the swell.
The formula is: Energy = 0.491 x Height² x Period². This means that both height and period significantly influence the result: a small wave with a long period can have more energy than a large wave with a short period.
- Less than 50 kJ: Low energy. Gentle waves, ideal for beginners.
- 50-150 kJ: Moderate energy. Good conditions for most surfers.
- 150-300 kJ: High energy. Powerful waves for experienced surfers.
- More than 300 kJ: Very high energy. Demanding conditions, experts only.
7. Forecast Score and Rating
Many forecast services (including WaveSearch) offer an overall score that summarizes all variables into a single number or rating. This makes decisions easier without having to analyze each piece of data separately.
In WaveSearch, the rating system works like this:
- Flat (1-2): Flat or nearly flat ocean. No surfable waves.
- Poor (3-4): Poor conditions. Small, messy waves or unfavorable wind.
- Fair (5-6): Acceptable conditions. Surfable but not ideal.
- Good (7-8): Good conditions. Well-shaped waves, adequate size, and favorable wind.
- Epic (9-10): Exceptional conditions. The kind of day you remember for years.
The rating is useful as a quick reference, but we recommend learning to read the individual data to make better decisions and understand why a day is rated a certain way.
8. Putting It All Together: The Perfect Forecast
Now that you understand each variable, let's see how to combine them to find the best time to surf:
Ideal day for a beginner:
- Height: 0.5 - 1.0m
- Period: 10-13 seconds
- Wind: Calm or light offshore (less than 10 km/h)
- Tide: Mid rising or mid falling
- Rating: Fair to Good (5-7)
Epic day for an experienced surfer:
- Height: 1.5 - 2.5m
- Period: 14-18 seconds
- Direction: SSW (for most Peruvian spots)
- Wind: Offshore 5-15 km/h
- Tide: Depends on the spot
- Rating: Good to Epic (8-10)
9. Common Mistakes When Reading Forecasts
- Only looking at height: A 1m day with a 15s period can be much better than a 2m day with 7s. Always check the period.
- Ignoring wind: The best waves of the year can be ruined if you surf at the wrong time with onshore wind.
- Not considering swell direction: Not all spots work with all swells. Learn which direction works best for your favorite beach.
- Blindly trusting the rating: The forecast is a prediction, not a guarantee. Local conditions (currents, bottom) can vary.
- Not checking the trend: Look not only at the current day but at the days before and after. A rising swell tends to be better than a declining one.
10. Use WaveSearch to Practice
The best way to learn to read a forecast is by practicing regularly. We suggest this routine:
- Before each session: Check the forecast on WaveSearch. Note the height, period, swell direction, and wind.
- During the session: Compare what you see in the water with what the forecast said. Are the waves the expected size? Is the wind as predicted?
- After the session: Reflect. Was the forecast accurate? What factors did you not consider?
Over time, you'll develop an intuition for reading forecasts and know exactly when to head to the beach. Set up custom alerts on WaveSearch to get notifications when conditions are ideal for your level and favorite spot.
Good waves and keep learning!