Guethary - Les Alcyons/Avalanche Surf Break

Lat Long: 43.43° N 1.62° W

Guethary - Les Alcyons/Avalanche Surf Forecast and Surf Report

Issued: 1 am 12 Aug 2026 (local time)

Forecast update in  hr  min

Today's Guethary - Les Alcyons/Avalanche sea temperature is
24.0° C
2.2° 

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 Aug 2026:

  • Best quality surf: Sunday 16 Aug, 5AM (local time) - 3.5ft (1.1m), 7s period, NW swell with glassy winds.
  • Most powerful swell: Sunday 16 Aug, 5PM (local time) - 4.5ft (1.3m), 8s period, NW swell with 227 kJ wave energy.
  • Next surfable swell (1★+): Sunday 16 Aug, 5AM (local time) - 3.5ft (1.1m), 7s 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 16) at 5AM. The primary swell is predicted to be 1.1m and 7s 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 1.3m 8s and forecast to arrive on Sunday (Aug 16) at 5PM. Winds are predicted to be onshore at the time the swell arrives.

Wave TypeTime (CEST) & Date Wave Height & Period
Next good surf (1 star+) 5AM (Sun 16th Aug)3.5ft (1.1m) 7s
Best Surf 5AM (Sun 16th Aug)3.5ft (1.1m) 7s
Most Powerful 5PM (Sun 16th Aug)4.5ft (1.3m) 8s

Table - best surf conditions forecast for Guethary - Les Alcyons/Avalanche over the next 16 days.


The Lowdown

Alright, this is Rusty. Let’s be real with you: the 16-day window for Guethary’s Les Alcyons/Avalanche is a tough watch. For the first week and a half, it’s pretty much flat to tiny, with mostly onshore or cross-onshore winds messing up what little there is. The real action doesn’t even start to build until the second week.

We kick off on Wednesday, August 12th, with a tiny 2ft swell from the NW, but the water is glassy in the morning with a 5 km/h WNW breeze. The water is 75°, which is 4° warmer than normal for this time of year – that’s a noticeable warm anomaly. Problem is, the waves are poor and weak, with combined energy at just 69. That’s the story through most of the first week: small, messy, and not worth paddling out for.

The first real glimmer shows up on Sunday, August 16th, in the afternoon. A 4ft NW swell hits, with a combined energy of 227 – that’s moderate. But the wind is onshore from the NW at 10 km/h, and the forecast calls it “marginal” at best. Still, it’s the first sign of life.

The real standout, the one you’ve been waiting for, arrives on Thursday, August 20th. The morning brings a 4ft NW groundswell with a period of 11 seconds, and combined energy jumps to 468 – that’s strong. The wind is light onshore, but the wave size and power are there. Friday, August 21st, pushes it further: a 6ft NW swell (period 10 seconds) with a huge 513 energy, but it’s still tagged as “marginal” due to conditions. That’s a solid expert-level swell at over 5ft, and with 6ft, it’s getting into the big stuff for the experienced crew only.

But the absolute best on offer? Look at Tuesday, August 25th, morning. A 4ft NW swell, period 9 seconds, combined energy of 216 (moderate), and the wind goes glassy offshore from the E at 10 km/h. That’s clean, it’s got push, and the wind will hold it open. For a reef break like this, with a 4ft NW swell and clean offshore conditions, that’s the call. Expect crowds to be likely – this spot is “often” packed.

Later on Thursday, August 27th, the swell bumps up to 8ft from the NW, with a combined energy of 733 (very strong). That’s expert-only territory, over 8ft, and with cross-onshore winds, it’s going to be a beast. Maybe one for the kite crew if you’re into that.

So, to wrap it up: the first week is a write-off. The second week builds nicely, but the standout is Tuesday, August 25th morning. That’s your window for clean, punchy reef waves at Les Alcyons/Avalanche. Get in early.

Rusty.

Short Range Forecast

Mostly dry. Warm (max 27°C on Wed afternoon, min 20°C on Fri morning). Wind will be generally light.

Days 4-6 Weather Summary

Light rain (total 7mm), mostly falling on Sat night. Warm (max 24°C on Mon afternoon, min 20°C on Sun night). Wind will be generally light.

Wednesday
12
Thursday
13
Friday
14
Saturday
15
Sunday
16
Monday
17
Tuesday
18
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
0.6
NW
8
0.4
WNW
10
0.4
WNW
9
0.5
W
10
0.4
WNW
10
0.6
WNW
11
0.8
WNW
10
0.6
WNW
10
0.6
WNW
9
0.7
WNW
9
0.8
NNW
6
1
NW
7
0.9
NW
8
1.3
NW
8
1.1
NW
8
0.9
NW
7
0.8
NW
7
0.8
NW
7
0.7
NW
6
0.6
NNW
6
0.6
NNW
6
Wave Graph
Metric surfscale
Energy kJ
57
34
28
50
32
93
111
74
66
71
49
94
109
227
141
86
73
55
38
22
22
Wind (km/h)
5
WNW
10
NNW
15
SW
5
NW
15
WNW
15
WSW
10
WNW
10
NW
10
W
10
NW
10
WNW
5
NW
10
WNW
10
NW
10
SW
10
W
10
WNW
15
W
10
WNW
15
NW
5
WNW
Wind State
glassy
on
cross
glassy
on
cross-on
cross-on
on
cross-on
on
on
glassy
cross-on
on
cross
cross-on
on
cross-on
on
on
glassy
High Tide
5:13PM4.01m
5:41AM3.78m
5:57PM4.15m
6:23AM3.83m
6:38PM4.16m
7:02AM3.79m
7:18PM4.05m
7:40AM3.68m
7:56PM3.82m
8:17AM3.50m
8:34PM3.53m
8:54AM3.28m
9:13PM3.21m
Low Tide
10:50AM0.23m
11:22PM-0.05m
11:34AM0.07m
00:05AM-0.14m
12:16PM-0.01m
00:46AM-0.12m
12:56PM0.03m
1:25AM0.01m
1:36PM0.16m
2:03AM0.24m
2:16PM0.38m
2:41AM0.52m
2:57PM0.65m
3:21AM0.82m
clear
clear
clear
clear
clear
clear
part cloud
part cloud
part cloud
part cloud
cloud
thunderstorm
part cloud
part cloud
thunderstorm
part cloud
rain showers
part cloud
part cloud
clear
part cloud
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
7:07
7:07
7:09
7:09
7:11
7:11
7:13
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
9:14
9:13
9:12
9:09
9:08
9:07
9:06
 mm
2
4
1
Temp °C
24
27
24
25
27
24
22
24
23
22
23
22
22
23
22
22
24
22
22
22
21
Feels °C
26
28
26
28
28
25
23
26
23
24
24
24
24
24
24
24
25
23
22
21
21
  • Map Icons:
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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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