Ever wondered why some surfers seem to score epic waves on the regular while others spend more time floundering in messy, shin-high waves?
It all comes down to your ability to decode surf conditions.
This is a fundamental skill of surfing (that many surf retreats don’t tell you about). But here at Xanadu, we want to make you a better surfer, not just better at surfing.
So, it’s time we dial up your Surf IQ.
Here’s a no-nonsense guide to surf conditions for anyone who doesn’t know what a “4–5 feet SW swell @ 15 secs” means.
What are “surf conditions” and why are they important?
“Surf conditions” is the umbrella term we use to describe all the natural forces that come together to form waves.
We could go really deep into surf conditions, but for the sake of getting you off the ground, we’ll touch on the basics. This includes:
- Swell (size and direction)
- Wave period
- Wind (offshore, onshore and cross-shore)
- Tide
Understanding surf conditions means you’re not relying on luck or hearsay (although they often come into play too).
By knowing how surf conditions influence the waves, you can make informed calls about when, where and what to surf.
A reliable surf forecast helps you stay safe by avoiding waves that are too big or heavy for your skill level. It also helps you pick the right board and the best time of day to paddle out.
So, whether you’re planning a Friday afternoon session or a mellow Monday morning sunrise surf, reading conditions is what transforms guesswork into confidence and ultimately… progress.
Surf conditions 101
Swell (size and direction)
Swell is the energy created by distant storms and winds blowing across the open ocean.
When that energy reaches the coastline, it transforms into the waves you see marching toward the shore.
The first thing to look at is swell height. This tells you the average size of the waves you can expect on a given day.
A forecasted swell height reflects the average from the trough (bottom) to the crest (peak) of the biggest one-third of waves measured over about 20 minutes.
Technical, for sure, but all you really need to know is that smaller swells (around 1–3 feet) are typically friendly and forgiving: ideal for beginners learning to pop up and trim along the face.
As the swell builds to 4–6 feet and beyond though, the waves pack more speed and power. This demands a higher level of skill and confidence.
- Smaller swells (1–3 ft): Great for learning and longboards
- Medium to large swells (4–6+ ft): More power, steeper shape, more challenge
Just as important as size is swell direction, which tells you the angle from which the swell is arriving at your spot.
This is usually shown in degrees or cardinal points like N, E, S or W or NW (north-west) or SSW (south-south-west). Every surf break has its preferred angles. For example, the south coast of Lombok prefers swells coming from a predominately southerly direction.
Essentially, swell direction determines whether the swell hits the local reefs square-on or misses them altogether.
Wave period
Swell height tells you how big the waves are. Wave period, on the other hand, tells you how powerful they are.
Let us explain.
Period is a unit of measurement represented by seconds. These seconds indicate the time between one wave and the next. The longer the wait, the more power the swell carries.
A wave every 11–20 seconds? That’s a powerful, long-period swell.
It means the energy has travelled far, is well-organised (aka clean) and will usually produce smooth, strong, surfable waves. These are the days where the sets roll in like clockwork, with shape, power and plenty of space between each ride.
Short-period swells (anything under 10 seconds) are the opposite.
They’re usually born from nearby winds that bring messy, weaker surf. Even if the swell height looks good on paper, a short period often means the lineup’s just a frothy soup of junky, choppy waves.
Case and point, conditions reading 2–3 feet @ 15 seconds will result in much bigger waves than conditions reading 4–5 feet @ 7 seconds. It all comes down to the period.
- 11–20+ sec = long period: More power, cleaner sets, better surf
- 10 sec or less = short period: Choppy, weak, wind-blown wave
Wind (offshore, onshore and cross-shore)
Wind can turn a perfect swell into magic conditions… or a total mess.
Offshore wind, blowing from land out to sea, is what we dream of (so long as it’s not too strong!). It holds the wave face up, making it smooth, clean and easier to ride.
Onshore wind is the opposite. It blows into the wave, crumbling the face and turning everything choppy, soupy and unpredictable. No bueno if you’re dreaming of perfectly peeling waves.
Then there’s cross-shore wind, which hits the wave from the side and can make things tricky depending on the strength and angle.
Last but not least, there’s also days when there’s no wind! This can be as good, if not better than if there’s a light offshore wind. At the very least, no wind makes carrying your longboard down to the water’s edge easier, right?
Offshore wind
- Holds up the wave face for longer rides
- Makes the surface clean and glassy
- Ideal for most breaks and all levels
Onshore wind
- Blows the wave down before it breaks
- Chops up the surface and ruins shape
- Makes takeoffs harder and rides more unpredictable
Cross-shore wind
- Blows across the wave at an angle
- Can create bumps or side-chop on the face
- Sometimes manageable, sometimes a dealbreaker (depends on strength and direction)
Tides (high, mid and low)
Tides refer to the regular rise and fall of the ocean, caused by the gravitational pull of the moon and the sun. There are two high tides and two low tides every day, but the exact timing shifts slightly each day.
Tides follow the moon’s cycle. During full and new moons, the pull from the moon and sun combine, creating spring tides (very high highs and very low lows).
During quarter moons, their pull works against each other, creating neap tides with smaller and more balanced shifts in water level.
These tidal changes have a big impact on surf. Depending on the break, tides can completely change the way a wave breaks or even stop it from breaking at all!
One hour can make a huge difference in wave quality, especially at sensitive spots like reef breaks or shallow sandbars.
For Lombok, we suggest picking your surf guide or instructor’s brain about the tides for a specific surf spot. Because our guides are locals, they know exactly how to time the best surf conditions based on the tides!
High tide
- Brings deeper water closer to shore
- Can soften waves or push them into the beach
- Often better for reef breaks and shallower setups
Mid-tide
- A balanced in-between with steady water movement
- Often offers the best combination of power and shape
Low tide
- Exposes more of the ocean floor
- Can create fast and hollow waves (or closeouts)
How do you know if surf conditions are good?
Sorry to break it to you, but there’s no single formula for perfect surf.
You can’t take what works for one break and apply it to another… even if those breaks are practically side-by-side!
What counts as “good” depends on your experience level, your board choice and the break you’re surfing.
Some spots only fire when a big swell lines up just right with the sandbars. Others work best on smaller swells with a mid-tide and a gentle offshore wind. Even two days that look similar on paper can feel totally different in the water.
That said, there’s a process to improve your chances of scoring. Here’s how to get closer to a yes before you even leave the house:
- Know your break’s preferences: First thing’s first… know what conditions your break favours! Does it like a straight south swell and mid-tide? If you don’t know yet, ask locals or keep notes after each session
- Check the surf forecast: Use websites like Windguru, Surf-Forecast or Surfline for your break. Look at swell height and direction, wave period, wind direction and strength and the tide
- Check the surf forecast… again: Checking one forecasting site isn’t enough. Forecasts vary depending on which buoy or model a particular site uses. Comparing two or three gives you a clearer read on the data
- Watch the webcams: If available! They give you real-time visual confirmation and not just numbers
- Trust your eyes: Conditions can shift fast. Always reassess when you get to the beach
The fastest way to truly understand what “good” looks like?
Spend several days in a row at the same spot. Multi-day surf retreats aren’t just about getting more waves… they also give you the chance to observe how conditions evolve hour by hour and day by day.
You’ll learn how tides, wind shifts and swell angles shape the surf in real time. That kind of knowledge builds confidence fast and allows you to surf independently around the world, whether you’re going it alone or as a couple.
And isn’t that what we’re all striving for?
Surf conditions FAQ
Q. What are the best surf conditions for beginners?
Small waves (1–3 ft), light offshore wind and mid to high tide are ideal. Look for long, mellow rides (not heavy or fast-breaking surf).
Q. Why does wind affect the waves so much?
Because it shapes the wave face. Offshore wind holds waves up and keeps them clean. Onshore wind pushes waves down and makes them messy and harder to ride. Cross-shore wind is somewhere in the middle.
Q. Is a bigger swell always better?
Not always. Bigger swells bring more power and size, but they can also mean heavier waves and tougher conditions. It depends on your skill level and the place you’re surfing.
Q. How far out can surf forecasts predict accurately?
Usually 3–5 days is reliable. After that, the info becomes less certain. Always check the forecast the night before and the surf report the morning of to access the most accurate data.
Q. What time of day is usually best to surf?
Early morning and late evening is often best here in Lombok. Winds are lighter, crowds are smaller and the ocean is typically cleaner and glassier (unless we’ve had strong on or cross-shore winds overnight!). Midday can still work depending on the spot, but mornings usually give you the best odds.
Want to become a surf forecasting pro?
Reading surf conditions is part science, part art. The more you learn about swell, wave period, wind and tides, the more confident you’ll feel as a surfer.
Again, booking a multi-day surf trip will accelerate your surf forecasting skills. There’s no substitute for back-to-back sessions when it comes to learning the ropes. You gain access to more experience in one week than you might in months of weekend trips.
Take it from us. We’ve helped a lot of surfers level up over the years. Thousands, in fact.
