Surf Forecasts:
Guethary - Les Alcyons/Avalanche surf forecast from 17 Aug 2026:
- Best quality surf: Friday 21 Aug, 11PM (local time) - 5ft (1.6m), 10s period, NW swell with glassy winds.
- Most powerful swell: Friday 21 Aug, 2AM (local time) - 5ft (1.6m), 11s period, NW swell with 579 kJ wave energy.
- Next surfable swell (1★+): Thursday 20 Aug, 11AM (local time) - 3.5ft (1.0m), 11s 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 11AM. The primary swell is predicted to be 1.0m and 11s 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 1.6m 11s and forecast to arrive on Friday (Aug 21) at 2AM. Winds are predicted to be cross-onshore at the time the swell arrives.
| Wave Type | Time (CEST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 11AM (Thu 20th Aug) | 3.5ft (1.0m) 11s |
| Best Surf | 11PM (Fri 21st Aug) | 5ft (1.6m) 10s |
| Most Powerful | 2AM (Fri 21st Aug) | 5ft (1.6m) 11s |
Table - best surf conditions forecast for Guethary - Les Alcyons/Avalanche over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let’s get straight into it. The only spot on the radar for this stretch is Guethary - Les Alcyons/Avalanche, a heavy reef setup that only suits the experts. Things are flat and quiet for a long while, so don't bother paddling out until we get some action.
The first few days are a write-off. Weak, choppy, and messy. We’re talking tiny swell with poor conditions through Monday 17th, Tuesday 18th, and Wednesday 19th. You’re looking at swell heights of 0.7 ft to 3 ft, all short-period windswell with combined energy that barely registers (62 or less). The water temp is sitting at 77°, which is a massive 6° warmer than normal – very unusual for this time of year.
The first real sign of life comes Thursday morning, 20th August. The glassy calm kicks in, and we get a cleaner 4 ft NW groundswell with a period of 11 seconds. The combined energy jumps to 281 (moderate). It’s not a standout, but at least it’s a start. Friday morning, 21st August, is similar with glassy conditions and 5 ft NW swell (444 energy), but scores are still low.
The pick of the entire 16-day window is a long way off, but it looks like a serious one. On Saturday morning, 29th August, the stars align. A massive 15 ft NW groundswell with a very long 14-second period rolls in. The combined energy rockets to 7039 – that’s very strong. And with glassy, offshore WSW wind at 0 mph, this reef is going to be pumping clean, powerful waves. Even with the afternoon wind turning onshore, the morning session is absolute perfection for experts only. Swell over 8 ft is for the experienced crew, and this one is a proper beast.
After that, Sunday 30th August stays solid with 8 ft NW swell and a 11-second period, though the wind swings cross-on, so it’ll be a bit messier. Expect crowds here often, especially on the big days, so get in early.
The rest of the run into early September sees plenty of size but poor quality wind, making it a tough paddle. The last call on Tuesday 1st September is still a solid 6 ft NW groundswell, but the onshore breezes will blow it out.
So, if you’re keen, pencil in Saturday 29th August. That’s the one to wait for. Everything else is either too small, too messy, or just not worth the paddle. Until then, keep the board in the bag.
Rusty.
Short Range ForecastLight rain (total 2mm), mostly falling on Wed night. Warm (max 24°C on Wed afternoon, min 19°C on Tue night). Wind will be generally light. | Days 5-7 Weather SummaryModerate rain (total 16mm), heaviest on Sat night. Warm (max 29°C on Sat afternoon, min 16°C on Fri night). Wind will be generally light. | |||||||||||||||||||
Mon 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | ||||||||||||||
PM | 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 6 | NW 6 | NW 7 | NNW 8 | NNW 6 | NW 6 | NNW 6 | NW 10 | NW 11 | NW 11 | NW 11 | NW 10 | NW 10 | NW 10 | NW 9 | NW 9 | NNW 8 | NW 7 | NW 7 | NW 7 |
Wave Graph  | ||||||||||||||||||||
 kJ | 25 | 31 | 17 | 45 | 12 | 9 | 6 | 51 | 233 | 293 | 579 | 513 | 475 | 465 | 235 | 176 | 175 | 91 | 33 | 18 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-on | glassy | cross-on | glassy | glassy | cross-on | on | glassy | on | cross-on | cross-on | glassy | off | cross-off | cross | glassy | cross-off | on | cross-off |
High Tide | 8:34PM3.53m | 8:54AM3.28m | 9:13PM3.21m | 9:33AM3.04m | 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 | |||||||
Low Tide | 2:16PM0.38m | 2:41AM0.52m | 2:57PM0.65m | 3:21AM0.82m | 3:43PM0.94m | 4:07AM1.12m | 4:39PM1.21m | 5:08AM1.36m | 5:56PM1.38m | 6:31AM1.47m | 7:27PM1.38m | 7:56AM1.39m | 8:39PM1.22m | |||||||
 |  | |  |  | | |  | | |  |  |  | | | |  | | | | |
 | — | — | 7:13 | — | — | 7:15 | — | — | 7:16 | — | — | 7:16 | — | — | 7:18 | — | — | 7:18 | — | — |
 | — | 9:07 | — | — | 9:06 | — | — | 9:04 | — | — | 9:01 | — | — | 9:00 | — | 8:59 | — | — | 8:58 | — |
mm | — | — | — | — | — | — | — | 2 | — | — | 5 | 2 | 3 | — | — | — | 6 | — | — | 1 |
Temp °C | 23 | 22 | 22 | 23 | 22 | 22 | 24 | 22 | 22 | 23 | 21 | 19 | 19 | 20 | 21 | 29 | 25 | 27 | 26 | 21 |
Feels °C | 24 | 24 | 25 | 24 | 23 | 25 | 24 | 23 | 24 | 24 | 21 | 20 | 20 | 21 | 19 | 29 | 26 | 28 | 26 | 22 |
Swell 1 Height (m) Direction Period (s) | NW 6 | NW 6 | NNW 5 | NNW 8 | NNW 6 | NW 6 | WNW 8 | NW 10 | NW 11 | NW 11 | NW 11 | NW 10 | NW 10 | NW 10 | NW 9 | NW 9 | NNW 8 | NW 7 | NW 7 | N 5 |
| kJ | 25 | 31 | 11 | 45 | 12 | 9 | 6 | 51 | 233 | 293 | 579 | 513 | 475 | 465 | 235 | 176 | 175 | 91 | 33 | 11 |
Swell 2 Height (m) Direction Period (s) | NW 8 | NW 8 | NW 7 | — | WNW 8 | WNW 8 | NW 11 | NW 7 | — | — | — | — | — | — | — | — | — | N 7 | WNW 8 | NW 7 |
| kJ | 20 | 14 | 17 | — | 7 | 6 | 5 | 11 | — | — | — | — | — | — | — | — | — | 32 | 7 | 18 |
Swell 3 Height (m) Direction Period (s) | — | NW 11 | — | — | — | — | N 7 | WNW 7 | — | — | — | — | — | — | — | — | — | WNW 9 | — | W 8 |
| kJ | — | 5 | — | — | — | — | 1 | 5 | — | — | — | — | — | — | — | — | — | 7 | — | 5 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | NNW 6 | — | — | — | — | — | — | — | — | — | — | — | N 6 | — |
| kJ | — | — | — | — | — | — | 6 | — | — | — | — | — | — | — | — | — | — | — | 27 | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 87 | 47 | 31 | 197 | 530 | 490 | 485 | 43 | 0 | 12 | 136 | 49 | 0 | 0 | 0 | 1 | 0 | 0 | 47 | 162 |
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.
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