Guethary - Les Alcyons/Avalanche Surf Break

Lat Long: 43.43° N 1.62° W

Guethary - Les Alcyons/Avalanche Surf Forecast and Surf Report

Issued: 7 pm 11 Sep 2026 (local time)

Forecast update in  hr  min

Today's Guethary - Les Alcyons/Avalanche sea temperature is
23.1°C
2.6° 

Guethary - Les Alcyons/Avalanche surf forecast is for near shore open water. Breaking waves will often be smaller at less exposed spots.


Guethary - Les Alcyons/Avalanche surf forecast from 12 Sep 2026:

  • Best quality surf: Sunday 13 Sep, 8AM (local time) - 4ft (1.2m), 13s period, NW swell with cross-offshore winds.
  • Most powerful swell: Friday 18 Sep, 11PM (local time) - 5.5ft (1.7m), 12s period, NW swell with 786 kJ wave energy.
  • Next surfable swell (1★+): Sunday 13 Sep, 5AM (local time) - 3ft (0.9m), 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 Sunday (Sep 13) at 5AM. The primary swell is predicted to be 0.9m and 10s period with a secondary swell of 0.4m and 14s. 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 1.7m 12s and forecast to arrive on Friday (Sep 18) at 11PM. Winds are predicted to be glassy at the time the swell arrives.

Wave TypeTime (CEST) & Date Wave Height & Period
Next good surf (1 star+) 5AM (Sun 13th Sep)3ft (0.9m) 10s
Best Surf 8AM (Sun 13th Sep)4ft (1.2m) 13s
Most Powerful11PM (Fri 18th Sep)5.5ft (1.7m) 12s

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’s on the cards for this stretch of coast. There’s only one spot in the mix for the whole 16-day window, and it’s a proper expert-only reef setup. So if you’re not on a shortboard and comfortable in heavy water, it might be one to watch from the cliff.

We’ve got a blank start. The first wave worth paddling out for isn’t until Sunday, September 13th. Before that, Saturday is a total write-off – tiny, weak, and messy. So you’ve got a day of waiting.

Alright, Sunday morning the 13th is where it kicks off. Guethary – Les Alcyons/Avalanche is going to be a standout. We’re looking at a clean 4ft groundswell out of the NW, with a period of 13 seconds – that’s proper long-period energy. The wind is dead calm, glassy as a mirror. The combined energy is a solid 545 – that’s moderate energy, but with that period it’ll feel punchy. This is a reef break, so that long period will line up beautifully and give you nice, bowling walls. Keep in mind, though, it’s an expert wave and crowds are often here, so expect some company on the peak. Water temp is about average for the time of year – nothing unusual.

Monday the 14th keeps the good times rolling in the morning – another glassy session with 4ft NW swell at 11 seconds and energy at 453. Nice and clean again. Tuesday and Wednesday drop off fast – the swell gets smaller and the wind turns onshore or cross-on and choppy. Thursday, September 17th morning is another real highlight. We’re up to 6ft NW, 12-second period, and glassy conditions. The energy jumps to 765 – getting into moderate-strong territory. That’s a serious morning for anyone with the skills to handle it.

Friday the 18th morning is also clean with 4ft. Then Saturday, September 19th morning is another banger: 6ft, 12 seconds, glassy, and energy at 760. That’s a weekend morning to circle.

Sunday the 20th morning is still clean at 4ft, but the afternoons get a bit bumpy. The pattern holds with clean mornings and grovelly afternoons through to Wednesday, September 23rd, where we get another standout morning: 5ft, 12 seconds, glassy, and energy at 583. Real clean.

Now, the big one. Friday, September 25th morning is the beast of the forecast. 8ft of NW groundswell with a 14-second period and combined energy of 2263 – that’s very strong. Glassy conditions again, offshore breeze. This is expert-only territory – way too big for anyone without serious experience. That’s the best looking day on the board, but it’s over a week away, so keep an eye on it.

After that, Saturday the 26th morning remains solid with 6ft and clean conditions. We finish on Sunday, September 27th morning with a lovely 3ft, 15-second groundswell and light offshore wind – clean as a whistle, though the energy dips to 488.

Overall, there are a lot of good mornings here, with Sunday the 13th, Thursday the 17th, Saturday the 19th, and Friday the 25th being the true standouts. Just remember, this spot is for experts, it’s often crowded, and it’s a reef. Pick your peaks wisely.

Rusty.

Short Range Forecast

Mostly dry. Warm (max 28°C on Mon afternoon, min 15°C on Sat morning). Wind will be generally light.

Days 5-7 Weather Summary

Light rain (total 2mm), mostly falling on Tue night. Warm (max 26°C on Mon night, min 16°C on Wed night). Wind will be generally light.

Saturday
12
Sunday
13
Monday
14
Tuesday
15
Wednesday
16
Thursday
17
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
1
0
0
0
3
1
3
2
0
2
0
0
0
0
0
3
3
1
2
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
0.9
NW
9
0.7
NW
8
0.7
WNW
8
0.5
NW
10
1.3
NW
13
1.3
NW
12
1.5
NW
12
1.3
NW
11
1.2
NW
11
1
NW
10
0.8
NW
10
0.6
NW
10
1.6
WNW
6
1.5
NW
7
1.4
NW
8
1.3
NW
10
1.7
NW
12
1.6
NW
11
1.3
NW
10
Wave Graph
Metric surfscale
Energy kJ
118
72
58
47
545
520
603
453
319
212
113
57
203
200
223
327
765
568
369
Wind (km/h)
5
SE
5
ENE
15
NNW
5
SW
0
NE
10
NNW
5
SSW
5
ENE
10
NNE
5
SE
10
W
25
W
20
NW
15
NW
15
NW
5
NE
5
NE
10
NW
5
WSW
Wind State
off
glassy
cross-on
cross
glassy
cross-on
glassy
glassy
cross-on
off
cross-on
cross-on
on
on
on
glassy
glassy
on
glassy
High Tide
5:57AM3.86m
6:12PM4.08m
6:32AM3.83m
6:48PM3.94m
7:05AM3.73m
7:21PM3.72m
7:37AM3.56m
7:55PM3.45m
8:09AM3.34m
8:29PM3.14m
8:44AM3.08m
9:09PM2.84m
Low Tide
11:40PM-0.11m
11:52AM-0.02m
00:16AM-0.07m
12:29PM0.02m
00:51AM0.08m
1:05PM0.15m
1:25AM0.30m
1:41PM0.37m
1:59AM0.57m
2:19PM0.65m
2:36AM0.87m
3:01PM0.94m
3:18AM1.17m
clear
clear
clear
clear
clear
clear
clear
clear
clear
clear
clear
clear
rain showers
cloud
part cloud
part cloud
part cloud
part cloud
part cloud
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
7:41
7:41
7:43
7:45
7:46
7:47
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
8:24
8:22
8:21
8:19
8:16
8:15
8:14
 mm
2
Temp °C
19
17
22
20
19
23
21
22
28
26
24
23
20
18
19
18
18
19
18
Feels °C
18
17
21
21
21
22
22
22
26
26
23
21
19
17
16
17
18
18
17
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  • Live Wave Height (m)
  • Live Wind Speed (km/h)
  • Surf Rating (10 Max)
  • Ocean Swells (m)
  • Wind Speed (km/h)
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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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