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 am 18 Aug 2026 (local time)

Forecast update in  hr  min

Today's Guethary - Les Alcyons/Avalanche sea temperature is
25.0° C
3.2° 

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 18 Aug 2026:

  • Best quality surf: Thursday 20 Aug, 8AM (local time) - 3.5ft (1.0m), 12s period, NW swell with cross-offshore winds.
  • Most powerful swell: Friday 21 Aug, 8AM (local time) - 5ft (1.6m), 10s period, NW swell with 503 kJ wave energy.
  • Next surfable swell (1★+): Thursday 20 Aug, 8AM (local time) - 3.5ft (1.0m), 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 8AM. The primary swell is predicted to be 1.0m and 12s period. 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 cross-onshore at the time the swell arrives.

Wave TypeTime (CEST) & Date Wave Height & Period
Next good surf (1 star+) 8AM (Thu 20th Aug)3.5ft (1.0m) 12s
Best Surf 8AM (Thu 20th Aug)3.5ft (1.0m) 12s
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, this is Rusty, and I’m looking at the next couple of weeks for our corner of the Basque coast. Let’s be honest with each other, it’s been a slow start. The ocean is just not giving us much to work with right now.

For the first few days, we’re looking at tiny, weak dribble. Tuesday the 18th and Wednesday the 19th are basically a write-off. The swell is knee-high at best, with short, weak periods and onshore winds. You’d be better off waxing your board and watching the horizon.

Things finally start to wake up on Thursday the 20th. The morning looks promising, with a glassy surface and a clean, long-period groundswell arriving from the NW. We’re talking about 4ft of swell from the west-northwest, with a solid 11-second period. It’s still not huge, but the wave energy is building to a moderate 304. For a high-performance reef like Guethary - Les Alcyons/Avalanche, this is the standout window. The water is 77°, which is much warmer than normal for this time of year, so you can leave the 4/3 at home. However, this is an expert-only reef break, and with the crowds listed as “often,” you won’t be alone out there.

The wind holds for Friday morning the 21st, but the swell is getting a bit more size at 5ft and a 10-second period. It’s a marginal call with a cross-on breeze. Saturday the 22nd morning cleans up nicely with light offshore winds from the ESE and a clean 4ft NW swell. That’s another solid window.

After that, the surf fades again through the end of August and the first few days of September. There’s a lot of flat, gutless days in there with no real quality.

Then, look at this – Thursday the 27th of August. A big pulse of energy is forecast, with the combined swell energy jumping to a very strong 1184. The morning is showing 8ft of WNW swell, but it’s coming with a fresh 19 mph cross-shore wind. That’s a lot of wind for an 8ft wave. It looks more like a day for the kite crew than a paddle surfer. A similar but slightly smaller swell follows on Friday the 28th and Saturday the 29th morning, which has cleaner conditions and 4ft waves.

Overall, the best bet is to pencil in Thursday the 20th and Saturday the 22nd mornings for the cleanest, most lined-up waves at Guethary. The big stuff later in the month is there, but it’s a battle with the wind.

Rusty.

Short Range Forecast

Light rain (total 4mm), mostly falling on Thu night. Warm (max 23°C on Tue afternoon, min 18°C on Wed morning). Wind will be generally light.

Days 4-6 Weather Summary

Moderate rain (total 19mm), heaviest on Sat morning. Warm (max 21°C on Fri night, min 16°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
Rating
(10 max)
0
0
0
0
0
0
2
0
1
1
0
2
2
0
1
1
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)
0.4
NW
7
0.5
NW
8
0.4
NW
7
0.4
NW
6
0.2
WNW
8
0.5
NW
13
1.1
NW
11
1.2
NW
11
1.4
NW
10
1.6
NW
10
1.6
NW
10
1.4
NW
10
1.2
NW
9
1.1
NW
9
1.1
NW
8
0.9
NW
8
0.8
NW
7
0.8
NW
7
1
NW
7
1.1
NW
7
0.7
NNW
6
Wave Graph
Metric surfscale
Energy kJ
17
33
13
9
6
83
304
319
400
475
465
384
235
172
153
101
65
77
89
100
32
Wind (km/h)
5
NNW
10
NNW
5
SW
5
W
15
NW
10
W
5
WSW
15
NNW
5
NNW
10
W
15
NNW
5
ESE
5
E
5
NNE
5
E
0
ESE
5
N
5
SW
0
ESE
10
WNW
15
WSW
Wind State
glassy
cross-on
glassy
cross-on
on
cross-on
glassy
cross-on
on
cross-on
on
glassy
cross-off
cross
cross-off
glassy
glassy
glassy
glassy
on
cross-on
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
part cloud
clear
clear
clear
clear
clear
part cloud
clear
light rain
part cloud
rain showers
rain showers
mod rain
light rain
cloud
cloud
cloud
light rain
rain showers
thunderstorm
rain showers
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
7:13
7:15
7:16
7:16
7:18
7:18
7:20
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
9:06
9:04
9:01
9:00
8:59
8:58
8:55
 mm
4
2
2
9
1
5
2
1
2
Temp °C
22
23
22
21
23
22
22
23
20
20
20
21
16
17
17
16
17
18
17
19
20
Feels °C
24
23
23
23
23
24
24
23
20
20
20
20
16
17
17
17
18
19
18
20
19
  • Map Icons:
  • Break
  • 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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