Surf Forecasts:
Guethary - Les Alcyons/Avalanche surf forecast from 18 Aug 2026:
- Best quality surf: Friday 21 Aug, 8AM (local time) - 5ft (1.6m), 10s period, NW swell with glassy winds.
- Most powerful swell: Friday 21 Aug, 8AM (local time) - 5ft (1.6m), 10s period, NW swell with 513 kJ wave energy.
- Next surfable swell (1★+): Thursday 20 Aug, 5AM (local time) - 2.5ft (0.7m), 12s 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 5AM. The primary swell is predicted to be 0.7m and 12s period with a secondary swell of 0.4m and 7s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Guethary - Les Alcyons/Avalanche in the next 16 days are 1.6m 10s and forecast to arrive on Friday (Aug 21) at 8AM. Winds are predicted to be glassy at the time the swell arrives.
| Wave Type | Time (CEST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 5AM (Thu 20th Aug) | 2.5ft (0.7m) 12s |
| Best Surf | 8AM (Fri 21st Aug) | 5ft (1.6m) 10s |
| Most Powerful | 8AM (Fri 21st Aug) | 5ft (1.6m) 10s |
Table - best surf conditions forecast for Guethary - Les Alcyons/Avalanche over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let's have a look at what Guethary's got cooking for us.
First up, it's been quiet for a few days, but we've got a solid window opening up from Thursday the 20th. That's when things start to look interesting. The water is running much warmer than usual for this time of year, sitting at 77°, so you might not even need a full suit.
Thursday morning the 20th is the first real standout. Guethary - Les Alcyons/Avalanche will be seeing a clean, glassy 4ft NW groundswell rolling in with a long period of 11 seconds. The combined energy is solid (304), and with glassy conditions and that long-period swell, the wave shape should be excellent on this reef setup. This is your window if you're an expert surfer. The wind swings onshore later in the day, so get on it early.
We get a bit of a messy spell from Friday through the weekend, with some cross-onshore wind and rain showers putting a damper on things. Saturday morning the 22nd is worth a mention though. We've got a 4ft NW swell with a clean ESE offshore wind blowing. The energy's moderate (241), and it should be a fun, clean session for those who don't mind a little light rain.
After that, the middle of next week turns quiet and small again, with only tiny, poor surf on offer.
Now, looking further ahead, the real prize might be on Tuesday the 1st of September. Mark it in your calendar, but don't hold your breath just yet. The forecast is showing a 5ft NW groundswell, period bumping up to 11 seconds, and the combined energy is pumping at 595. But the best part? Glassy, dead-calm conditions with some clouds in the morning. This is a promising long-range call for exceptional waves at the reef. Wednesday the 2nd morning also looks strong with clean 5ft NW swell and offshore ESE wind. Things get blown out by Wednesday afternoon, though.
If you're an expert and can wait, the first days of September look like the payoff. Otherwise, that Thursday morning is your best bet in the near term.
Rusty.
Short Range ForecastLight rain (total 7mm), mostly falling on Thu night. Warm (max 24°C on Tue afternoon, min 18°C on Thu night). Wind will be generally light. | Days 4-6 Weather SummaryModerate rain (total 12mm), heaviest on Sat afternoon. Warm (max 20°C on Fri afternoon, min 17°C on Fri night). Wind will be generally light. | ||||||||||||||||||||
Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | |||||||||||||||
AM | 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 7 | NW 8 | NW 7 | NW 6 | NNW 6 | NW 13 | NW 11 | NW 11 | NW 10 | NW 10 | NW 10 | NW 10 | NW 9 | NW 9 | NW 8 | NW 8 | NW 8 | NW 7 | NW 7 | NNW 6 | NNW 6 |
Wave Graph  | |||||||||||||||||||||
 kJ | 17 | 33 | 13 | 9 | 6 | 83 | 304 | 287 | 478 | 475 | 465 | 384 | 241 | 172 | 129 | 86 | 55 | 34 | 46 | 51 | 25 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | cross-on | glassy | glassy | on | cross-on | glassy | on | cross-on | cross-on | cross-on | cross-off | off | cross-off | glassy | cross-off | glassy | glassy | cross-on | cross-on | cross-off |
High Tide | 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 | 3:24PM2.96m | 3:51AM2.93m | |||||||
Low Tide | 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 | 8:57AM1.19m | 9:30PM0.99m | ||||||||
 |  |  | | |  | | |  |  |  | | | |  |  | |  | |  | | |
 | 7:13 | — | — | 7:15 | — | — | 7:16 | — | — | 7:16 | — | — | 7:18 | — | — | 7:18 | — | — | 7:20 | — | — |
 | — | — | 9:06 | — | — | 9:04 | — | — | 9:01 | — | — | 9:00 | — | 8:59 | — | — | 8:58 | — | — | 8:55 | — |
mm | — | — | — | — | — | 1 | — | — | 6 | 1 | 1 | 1 | 2 | 3 | — | — | 2 | 2 | 2 | 1 | — |
Temp °C | 22 | 24 | 22 | 21 | 23 | 21 | 21 | 23 | 21 | 18 | 20 | 19 | 17 | 17 | 17 | 18 | 20 | 19 | 20 | 22 | 21 |
Feels °C | 24 | 25 | 23 | 23 | 24 | 22 | 23 | 24 | 21 | 19 | 20 | 19 | 17 | 17 | 18 | 19 | 21 | 20 | 19 | 20 | 21 |
Swell 1 Height (m) Direction Period (s) | NNW 6 | NW 8 | NW 7 | NW 6 | NNW 6 | NW 13 | NW 11 | NW 11 | NW 10 | NW 10 | NW 10 | NW 10 | NW 9 | NW 9 | NW 8 | NW 8 | NW 8 | NW 7 | NW 7 | NNW 6 | NNW 6 |
| kJ | 12 | 33 | 13 | 9 | 6 | 83 | 304 | 287 | 478 | 475 | 465 | 384 | 241 | 172 | 129 | 86 | 55 | 34 | 46 | 51 | 25 |
Swell 2 Height (m) Direction Period (s) | NW 7 | — | NNW 5 | WNW 8 | WNW 8 | NW 7 | — | — | — | — | — | — | — | — | — | — | — | — | W 8 | W 8 | W 4 |
| kJ | 17 | — | 5 | 6 | 6 | 12 | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 1 | 1 |
Swell 3 Height (m) Direction Period (s) | — | — | WNW 8 | — | NW 11 | WNW 7 | — | — | — | — | — | — | — | — | — | — | — | — | — | NW 10 | W 8 |
| kJ | — | — | 7 | — | 5 | 5 | — | — | — | — | — | — | — | — | — | — | — | — | — | 4 | 1 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| kJ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 111 | 606 | 526 | 493 | 495 | 13 | 0 | 12 | 12 | 12 | 87 | 0 | 0 | 0 | 0 | 1 | 3 | 21 | 196 | 197 | 56 |
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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