Surf Forecasts:
Guethary - Les Alcyons/Avalanche surf forecast from 22 Aug 2026:
- Best quality surf: Saturday 29 Aug, 2AM (local time) - 8ft (2.5m), 10s period, WNW swell with cross-offshore winds.
- Most powerful swell: Saturday 29 Aug, 2AM (local time) - 8ft (2.5m), 10s period, WNW swell with 1,508 kJ wave energy.
- Next surfable swell (1★+): Sunday 23 Aug, 2AM (local time) - 3.5ft (1.0m), 8s period with NW swell.
Best Forecast Surf Conditions for Guethary - Les Alcyons/Avalanche this week:
The surf forecast for Guethary - Les Alcyons/Avalanche over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Sunday (Aug 23) at 2AM. The primary swell is predicted to be 1.0m and 8s period. The wind is predicted to be offshore as the swell arrives.
The most powerful waves expected at Guethary - Les Alcyons/Avalanche in the next 16 days are 2.5m 10s and forecast to arrive on Saturday (Aug 29) at 2AM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 4s period and expected on Friday (Aug 28) at 8AM.
| Wave Type | Time (CEST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 2AM (Sun 23rd Aug) | 3.5ft (1.0m) 8s |
| Best Surf | 2AM (Sat 29th Aug) | 8ft (2.5m) 10s |
| Most Powerful | 2AM (Sat 29th Aug) | 8ft (2.5m) 10s |
Table - best surf conditions forecast for Guethary - Les Alcyons/Avalanche over the next 16 days.
The Lowdown
Alright, let’s get into it. The next couple of weeks are a bit of a mixed bag around here. We’ve got some solid potential building towards the end of the month and into early September, but you’re going to have to sit through a fair bit of flat, sloppy, or just plain ordinary conditions before the good stuff shows up.
Looking at the whole picture, the standout window is shaping up for the very end of the month and into the first week of September. The rest of the time is a write-off for anything decent, with a long stretch of poor surf and very little to get excited about.
So, here’s the rundown:
We start off with a long, quiet spell. From now through the 27th of August, there’s nothing worth paddling out for. The swell is tiny, the period is short, and the energy is weak. We’re talking about small, messy waves with barely any push. The winds are all over the place, but mostly cross or onshore, keeping things chopped up. It’s a real dry spell in the surf department.
Then, on Friday the 28th of August, we finally see a pulse of energy. The swell picks up to around 6 ft from the WNW, with a period of 10 seconds and moderate energy (599). The catch? The wind is cross-onshore, so it’s going to be a bit bumpy. The conditions are marginal, and the tide might not be playing ball either. It’s a “maybe” session for the keen, but not a standout.
Saturday the 29th of August, the swell builds further. We’re looking at 8 ft from the WNW, with a period of 10 seconds, and the energy is strong (1207). But again, the wind is cross-onshore, and the forecast says it’s marginal. That’s a fair bit of size, so it’s going to be heavy and probably a bit messy. This is expert territory only, and only if you’re willing to deal with the chop.
Now, here’s where it gets interesting. Sunday the 30th of August morning is, without a doubt, the best call in the whole outlook. The swell drops back to a more manageable 4 ft from the NW, period is 8 seconds, and the energy is moderate (250). But the real magic is the wind: glassy, with a slight air from the ENE. That’s going to give you clean, smooth waves at Guethary - Les Alcyons/Avalanche. This is a reef break, consistent, and it’s an expert wave, so it’s not one for the beginners. The swell is coming from the W, which is the optimum direction for this spot. The water temp is about average for this time of year. It’s the one session in the whole window that looks genuinely good. The crowd factor is “often” here, so expect some company, but for conditions like that, it’s worth it.
After that, the 31st of August and the 1st of September see the swell drop back down and the wind turning onshore or cross-onshore, killing the quality. It’s back to poor surf.
Then there’s another gap. From the 2nd of September through the 5th of September, it’s small, weak, and mostly messy. The swell is barely there, and the wind is consistently onshore or cross-onshore. Nothing to see here.
The final glimmer is on Monday the 7th of September morning. We get a clean, 4 ft swell from the NW with a long period of 12 seconds (452 energy). The wind is light and cross-offshore from the E, so the surface will be clean. This is a long-period groundswell, which means better shaped waves and more energy, but it can be a bit straight at beach breaks. For a reef like Les Alcyons/Avalanche, this should be a good match. It’s a promising session, but it’s a long way out, so keep an eye on it.
So, to sum it up: the best bet is Sunday morning the 30th of August for glassy, clean waves at the reef. The Monday morning the 7th of September is also worth keeping on the radar for a clean, long-period swell. Everything else is a struggle.
Rusty.
Short Range ForecastModerate rain (total 12mm), heaviest on Sun night. Warm (max 31°C on Mon afternoon, min 19°C on Sun morning). Wind will be generally light. | Days 5-7 Weather SummarySome drizzle, heaviest during Thu night. Warm (max 31°C on Wed afternoon, min 17°C on Thu night). Wind will be generally light. | ||||||||||||||||||
Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | Thursday 27 | Friday 28 | ||||||||||||||
Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | |
Swell Height Map | |||||||||||||||||||
Wave Height (m) Direction Period (s) | NW 8 | NW 7 | NW 7 | N 5 | N 5 | NNW 7 | WNW 3 | NW 13 | NW 12 | NW 11 | NW 10 | NW 10 | NW 9 | WNW 5 | WNW 9 | WNW 9 | WNW 10 | WNW 10 | WNW 10 |
Wave Graph | |||||||||||||||||||
129 | 56 | 26 | 17 | 5 | 4 | 2 | 7 | 23 | 31 | 36 | 24 | 30 | 32 | 190 | 212 | 590 | 778 | 1508 | |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | off | glassy | cross | off | cross-off | cross | off | cross | cross-on | cross-off | off | cross-off | cross-off | cross | on | cross-off | cross-on | on | cross-off |
High Tide | 2:03AM2.54m | 2:31PM2.73m | 3:07AM2.71m | 3:24PM2.96m | 3:51AM2.93m | 4:05PM3.21m | 4:26AM3.14m | 4:39PM3.45m | 4:59AM3.34m | 5:10PM3.65m | 5:29AM3.50m | 5:41PM3.80m | |||||||
Low Tide | 7:56AM1.39m | 8:39PM1.22m | 8:57AM1.19m | 9:30PM0.99m | 9:43AM0.95m | 10:11PM0.74m | 10:20AM0.71m | 10:46PM0.50m | 10:54AM0.49m | 11:18PM0.31m | 11:26AM0.32m | 11:50PM0.17m | |||||||
— | 7:18 | — | — | 7:20 | — | — | 7:20 | — | — | 7:22 | — | — | 7:24 | — | — | 7:24 | — | — | |
8:59 | — | 8:58 | — | — | 8:55 | — | — | 8:53 | — | — | 8:52 | — | — | 8:51 | — | — | 8:49 | — | |
mm | 6 | — | — | 6 | — | — | — | — | — | — | — | — | — | — | — | 1 | — | — | — |
Temp °C | 25 | 24 | 30 | 27 | 27 | 31 | 26 | 26 | 25 | 22 | 24 | 31 | 27 | 23 | 26 | 22 | 20 | 23 | 21 |
Feels °C | 25 | 27 | 29 | 27 | 28 | 28 | 25 | 25 | 23 | 24 | 24 | 30 | 26 | 21 | 23 | 22 | 19 | 20 | 20 |
Swell 1 Height (m) Direction Period (s) | NW 8 | NW 7 | NW 7 | N 5 | N 5 | NNW 7 | WNW 3 | NW 13 | NW 12 | NW 11 | NW 5 | NW 5 | NW 9 | NW 8 | WNW 9 | WNW 9 | WNW 10 | WNW 10 | WNW 10 |
129 | 56 | 26 | 17 | 4 | 4 | 1 | 7 | 23 | 31 | 10 | 7 | 20 | 18 | 190 | 212 | 590 | 778 | 1508 | |
Swell 2 Height (m) Direction Period (s) | — | W 8 | W 8 | NW 7 | NNW 7 | — | NW 6 | NW 4 | W 8 | NW 4 | NW 10 | NW 10 | — | — | — | WNW 12 | — | — | — |
— | 6 | 1 | 13 | 5 | — | 2 | 1 | 1 | 2 | 36 | 24 | — | — | — | 119 | — | — | — | |
Swell 3 Height (m) Direction Period (s) | — | — | W 12 | W 10 | W 9 | W 9 | N 5 | N 6 | W 9 | W 8 | — | — | — | — | — | — | — | — | — |
— | — | 3 | 2 | 2 | 2 | 1 | 1 | 1 | 1 | — | — | — | — | — | — | — | — | — | |
Wind waves Height (m) Direction Period (s) | — | — | N 5 | — | — | NNW 5 | — | SW 3 | NW 3 | — | — | — | WNW 4 | WNW 5 | W 4 | — | SW 4 | — | — |
— | — | 5 | — | — | 2 | — | 1 | 1 | — | — | — | 30 | 32 | 9 | — | 9 | — | — | |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 0 | 1 | 264 | 31 | 347 | 304 | 313 | 460 | 534 | 31 | 1 | 21 | 3 | 113 | 49 | 0 | 12 | 147 | 0 |
Best forecast wave conditions in La Cote Basque | |||||||||||||||||||
Best forecast wave conditions in France | |||||||||||||||||||
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Information about the Guethary - Les Alcyons/Avalanche Surf forecast
The above surf forecast table for Guethary - Les Alcyons/Avalanche provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Guethary - Les Alcyons/Avalanche can be found by selecting the local surf guide option on the grey menu. Our Guethary - Les Alcyons/Avalanche surf forecast is unique since it includes wave energy (power) that defines the real feel of the surf rather than just the height or the period. If you surf the same spot (Guethary - Les Alcyons/Avalanche) regularly then make a mental note of the wave energy from the surf forecast table each time you go. Very soon you may start to choose your surf days based on the wave energy alone combined with our forecast of favourable offshore wind conditions. Our star ratings will help here and of course you will also find the usual wave height and period predictions on our surf forecasts as well as a full break down of the swell components under our advanced users option (to reveal that, click the little Einstein character under the tide times).
Further information to help with frequently asked questions about our surf forecast for Guethary - Les Alcyons/Avalanche may be found under the help tab on the top menu and also by moving your mouse over the question marks on the surf forecast table itself. Please always bear in mind that the forecast is for near-shore open water and local factors at each surf break influence the actual breaking wave height, such as the beach / reef profile, water depths offshore and shelter.
Guethary - Les Alcyons/Avalanche is 9 km (6 miles) from Biarritz. If you plan a holiday in La Cote Basque, look for hotels and other accommodation in Biarritz. Biarritz has rooms for a wide range of budgets as well as car hire and transport links.











