Surf Forecasts:
Guethary - Les Alcyons/Avalanche surf forecast from 20 Aug 2026:
- Best quality surf: Friday 21 Aug, 11PM (local time) - 5ft (1.6m), 10s period, NW swell with glassy winds.
- Most powerful swell: Thursday 27 Aug, 2AM (local time) - 8ft (2.4m), 9s period, WNW swell with 893 kJ wave energy.
- Next surfable swell (1★+): Thursday 20 Aug, 8PM (local time) - 4.5ft (1.3m), 10s 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 Thursday (Aug 20) at 8PM. The primary swell is predicted to be 1.3m and 10s period. The wind is predicted to be glassy as the swell arrives.
The most powerful waves expected at Guethary - Les Alcyons/Avalanche in the next 16 days are 2.4m 9s and forecast to arrive on Thursday (Aug 27) at 2AM. Winds are predicted to be glassy at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Tuesday (Aug 25) at 8AM.
| Wave Type | Time (CEST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 8PM (Thu 20th Aug) | 4.5ft (1.3m) 10s |
| Best Surf | 11PM (Fri 21st Aug) | 5ft (1.6m) 10s |
| Most Powerful | 2AM (Thu 27th Aug) | 8ft (2.4m) 9s |
Table - best surf conditions forecast for Guethary - Les Alcyons/Avalanche over the next 16 days.
The Lowdown
G’day, Rusty here, and I’ve been staring at the charts for Guethary - Les Alcyons/Avalanche. This is a reef break, expert territory, and it’s consistent. The water temperature is about average for this time of year, nothing wild.
The next couple of weeks look like a real mixed bag. We’ve got a lot of wind and onshore junk to work through, but there are a couple of windows that’ll get the blood pumping.
This Thursday morning (20th August) is a write-off. We’ve got a 4 ft NW swell (384) but it’s cross-on with a 10 km/h W wind, and the report says poor. Not worth paddling out. The afternoon and most of Friday stay average with rain and onshore winds, swell bumping up to 6 ft (724) on Friday morning but still onshore and messy.
Saturday morning the 22nd of August, things start to shift. The wind swings east at 15 km/h, going cross-offshore, and the 4 ft NW swell (269) is coming in clean. That’s a solid option for a relaxed session, but it’s small. By the afternoon, the wind picks up and the quality drops.
Sunday the 23rd through to Tuesday the 25th is a brutal stretch. Swell drops under 3 ft, energy falls to 37-15, and winds are all over the place. It’s a quiet spell, dead in the water for a few days.
Wednesday morning the 26th of August shows a glimmer – a 3 ft WNW swell (82) with a 5 km/h SSE wind going glassy off. Clean, but tiny. Worth a paddle if you’re desperate.
Thursday afternoon the 27th of August, the swell starts to ramp up hard. We’re looking at 10 ft WNW swell (1364) with a 20 km/h onshore wind. That’s a big, powerful groundswell, but the wind is on it, and the period is short at 9 seconds. Marginal at best, and 10 ft is expert-only territory.
Friday the 28th of August morning sees 7 ft WNW swell (788) with cross-on winds. Still lumpy. The real standout is shaping up for Saturday morning the 29th of August. We’ve got 7 ft NW swell (634) with a light 10 km/h W cross-on breeze. The report says marginal, but it’s the best of the big stuff. Sunday morning the 30th of August, the wind goes glassy with a 5 km/h ESE breeze, and the swell is 5 ft from the NW (370). That’s clean, lined-up, and perfect for the reef. That’s the one to aim for.
Monday morning the 31st of August is also clean with a 5 ft NW swell (330) and E cross-off winds. Solid.
The week after that, from Tuesday 1st September, the swell holds around 5-6 ft (338-461) but the wind is mostly cross-on or onshore. Wednesday the 2nd of September has a 7 ft NW swell (697) in the afternoon, but again, cross-on winds.
Now, the true standout: Thursday morning the 3rd of September. This is a cracker. We’ve got a 7 ft NW swell (880) with a 5 km/h ENE cross-off wind. The report says “expect very good surf conditions.” The energy is strong (880), the wind is light offshore, and the period is 10 seconds – a nice groundswell. This is the best session on offer for the reef, but it’s expert-only at that size. The crowd factor is “often” there, so expect company.
Friday morning the 4th of September drops back to 5 ft WNW (385) with light cross-on winds – marginal.
So if you’re picking a highlight, lock in Thursday morning 3rd September at Les Alcyons/Avalanche. Clean, 7 ft NW swell, light offshore wind. That’s a proper day.
Rusty.
Short Range ForecastModerate rain (total 15mm), heaviest on Thu night. Warm (max 28°C on Sat afternoon, min 15°C on Sat morning). Wind will be generally light. | Days 5-7 Weather SummaryModerate rain (total 10mm), heaviest on Sat night. Warm (max 33°C on Mon afternoon, min 18°C on Sun morning). Wind will be generally light. | ||||||||||||||||||
Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | ||||||||||||||
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 13 | NW 11 | NW 11 | NW 10 | NW 10 | NW 10 | NW 10 | NW 9 | NW 9 | NW 8 | NW 8 | NW 7 | NW 7 | NW 7 | NNW 6 | N 4 | SW 4 | NW 3 | WNW 9 |
Wave Graph | |||||||||||||||||||
83 | 384 | 357 | 384 | 724 | 569 | 465 | 269 | 172 | 147 | 57 | 26 | 13 | 11 | 11 | 4 | 8 | 6 | 32 | |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | on | cross | on | on | cross-off | cross-off | cross | cross-off | cross-off | cross-on | glassy | cross-off | on | cross-off | cross | cross-on | cross-off |
High Tide | 9:57PM2.89m | 10:21AM2.81m | 10:56PM2.63m | 11:31AM2.63m | 00:26AM2.48m | 1:09PM2.59m | 2:03AM2.54m | 2:31PM2.73m | 3:07AM2.71m | 3:24PM2.96m | 3:51AM2.93m | 4:05PM3.21m | 4:26AM3.14m | ||||||
Low Tide | 4:07AM1.12m | 4:39PM1.21m | 5:08AM1.36m | 5:56PM1.38m | 6:31AM1.47m | 7:27PM1.38m | 7:56AM1.39m | 8:39PM1.22m | 8:57AM1.19m | 9:30PM0.99m | 9:43AM0.95m | 10:11PM0.74m | |||||||
— | 7:16 | — | — | 7:16 | — | — | 7:18 | — | — | 7:18 | — | — | 7:20 | — | — | 7:20 | — | — | |
9:04 | — | — | 9:01 | — | — | 9:00 | — | 8:59 | — | — | 8:58 | — | — | 8:55 | — | — | 8:53 | — | |
mm | — | — | 3 | 5 | 4 | 3 | — | — | — | 9 | 1 | — | — | — | — | — | — | — | — |
Temp °C | 22 | 22 | 21 | 20 | 20 | 21 | 21 | 20 | 28 | 25 | 22 | 31 | 30 | 28 | 33 | 26 | 25 | 26 | 22 |
Feels °C | 24 | 23 | 21 | 20 | 19 | 20 | 20 | 18 | 25 | 26 | 23 | 30 | 30 | 29 | 31 | 26 | 22 | 24 | 21 |
Swell 1 Height (m) Direction Period (s) | NW 13 | NW 11 | NW 11 | NW 10 | — | NW 10 | NW 10 | NW 9 | NW 9 | NW 8 | NW 8 | NW 7 | N 5 | N 5 | NNW 6 | N 4 | NW 6 | NW 12 | WNW 9 |
83 | 384 | 357 | 384 | — | 569 | 465 | 269 | 172 | 147 | 57 | 26 | 10 | 9 | 11 | 4 | 1 | 6 | 32 | |
Swell 2 Height (m) Direction Period (s) | NNW 7 | — | — | — | — | — | — | — | — | — | W 9 | W 8 | NW 7 | NW 7 | W 9 | W 3 | NW 14 | SW 4 | NW 4 |
5 | — | — | — | — | — | — | — | — | — | 6 | 6 | 13 | 11 | 2 | 1 | 7 | 1 | 3 | |
Swell 3 Height (m) Direction Period (s) | WNW 7 | — | — | — | — | — | — | — | — | — | — | — | W 10 | W 9 | W 10 | NW 6 | NW 9 | NW 8 | NW 11 |
5 | — | — | — | — | — | — | — | — | — | — | — | 2 | 2 | 2 | 2 | 3 | 3 | 19 | |
Wind waves Height (m) Direction Period (s) | NW 4 | — | — | — | NW 10 | — | — | — | N 3 | — | — | N 5 | — | — | — | — | SW 4 | NW 3 | — |
5 | — | — | — | 724 | — | — | — | 5 | — | — | 5 | — | — | — | — | 8 | 5 | — | |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 39 | 12 | 12 | 6 | 49 | 12 | 0 | 0 | 69 | 0 | 1 | 222 | 47 | 162 | 189 | 279 | 356 | 606 | 1 |
Best forecast wave conditions in La Cote Basque | |||||||||||||||||||
Best forecast wave conditions in France | |||||||||||||||||||
Header Global | |||||||||||||||||||
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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.











