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 pm 12 Sep 2026 (local time)

Forecast update in  hr  min

Today's Guethary - Les Alcyons/Avalanche sea temperature is
23.0°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: Friday 18 Sep, 11PM (local time) - 6ft (1.9m), 14s period, NW swell with cross-offshore winds.
  • Most powerful swell: Saturday 19 Sep, 5AM (local time) - 7ft (2.2m), 14s period, NW swell with 1,719 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 2.2m 14s and forecast to arrive on Saturday (Sep 19) at 5AM. Winds are predicted to be offshore 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 Surf11PM (Fri 18th Sep)6ft (1.9m) 14s
Most Powerful 5AM (Sat 19th Sep)7ft (2.2m) 14s

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


The Lowdown

Alright, Rusty here. Let’s have a look at what’s coming our way.

Right now, there’s not a lot to get excited about. We’ve got a bit of a slow start. Saturday afternoon the 12th is flat and messy, so just sit tight. The real action doesn’t kick in until Sunday morning the 13th.

Guethary - Les Alcyons/Avalanche is the only spot we’re looking at. It’s a reef break that needs an expert touch. That first proper window is Sunday morning the 13th. The water temperature is 73°, which is much warmer than normal for this time of year – a good 5° above average, so you can leave the thick rubber at home. We’ve got a 4ft groundswell from the NW with a solid 13-second period. The combined swell energy is moderate (545). The real magic here is the glassy offshore wind from the NE. That’s going to make for some beautifully clean waves at this exposed reef. It will be bigger than Saturday, and the quality is top-notch. Expect long-period groundswell, which means longer waits between sets, but the waves themselves will have plenty of power. This is the standout of the whole run. Crowds are likely here, so get out early.

Monday morning the 14th offers similar 4ft NW swell with glassy ENE winds, though the period drops to 11 seconds and the energy to 453. It’s still very good, just a notch below Sunday.

The middle of the week turns average. Tuesday and Wednesday get messy with cross-onshore winds and shorter period swell. Not worth the paddle out. Conditions remain poor through the rest of the week until Friday afternoon the 18th, when we get a glassy window with a 4ft NW swell at 9 seconds (285 energy). It’s a smaller, cleaner option for a late session.

Now, keep your eyes on Saturday morning the 19th. This is another standout, but for experienced surfers only. A 7ft NW groundswell with a 13-second period and absolutely glassy conditions. The combined energy jumps to a strong 1395. This is a big, powerful swell and it will be clean. At over 7ft, it’s strictly for the experts. The wind is calm, the waves will be lined up, but that reef will be handling a lot of water.

Monday morning the 21st is similar in quality. We get a 7ft NW groundswell at 14 seconds with a light cross-offshore wind from the east, keeping it clean. The energy is a very strong 1528. Another one for the experienced crew.

Tuesday morning the 22nd might be the biggest pulse. A 8ft NW groundswell at 13 seconds with a light cross-offshore wind. The energy is a massive 1862. Again, this is expert territory. The morning windows are the ones to chase during this second week.

Beyond that, it slowly fades out. Wednesday morning the 23rd is still clean with a 5ft swell, but it drops off after that. The following weekend looks poor.

So to sum it up: the two absolute standouts are Sunday morning the 13th for clean, quality waves in the shoulder-high range, and Saturday morning the 19th for a bigger, more powerful swell in clean conditions. The first one is for everyone comfortable on a reef, the second is only for the experts. Get on it.

Rusty

Short Range Forecast

Mostly dry. Warm (max 28°C on Mon afternoon, min 16°C on Sun morning). Wind will be generally light.

Days 5-7 Weather Summary

Light rain (total 3mm), mostly falling on Tue night. Warm (max 23°C on Tue afternoon, min 16°C on Fri morning). Wind will be generally light.

Sat
12
Sunday
13
Monday
14
Tuesday
15
Wednesday
16
Thursday
17
Friday
18
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
3
2
3
2
1
2
0
0
0
0
0
2
2
1
1
1
2
4
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
0.7
WNW
8
0.5
NW
10
1.3
NW
13
1.3
NW
12
1.5
NW
12
1.3
NW
11
1.1
NW
11
1
NW
10
0.8
NW
10
1.3
WNW
5
1.3
WNW
6
1.4
NW
7
1.6
NW
8
1.6
NW
10
1.8
NW
11
1.7
NW
11
1.4
NW
10
1.1
NW
10
1.1
NW
9
2.1
NW
14
Wave Graph
Metric surfscale
Energy kJ
58
47
545
520
593
453
286
212
115
85
145
192
358
509
703
651
388
204
183
1641
Wind (km/h)
15
NNW
5
SSW
5
NE
10
NNW
5
SSW
5
ENE
10
N
5
S
10
WNW
25
W
15
WNW
15
NW
15
NNW
10
N
5
NNW
15
NW
10
W
10
W
5
NW
5
SE
Wind State
cross-on
cross-off
glassy
cross-on
cross-off
glassy
cross-on
cross-off
cross-on
cross-on
on
on
on
cross-on
on
on
cross-on
cross-on
glassy
off
High Tide
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
9:27AM2.82m
10:03PM2.57m
Low Tide
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
3:54PM1.23m
4:17AM1.42m
clear
clear
clear
clear
clear
clear
clear
clear
clear
clear
rain showers
light rain
clear
part cloud
part cloud
part cloud
part cloud
cloud
part cloud
clear
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
7:41
7:43
7:45
7:46
7:47
7:48
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
8:22
8:21
8:19
8:16
8:15
8:14
8:12
 mm
1
2
Temp °C
22
20
20
24
21
22
28
24
23
23
21
19
19
18
19
19
18
17
19
18
Feels °C
21
21
21
23
22
21
26
24
22
22
21
18
16
16
18
17
17
16
20
19
  • 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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