Avellanas Rivermouth Surf Break

Lat Long: 10.24° N 85.84° W

Avellanas Rivermouth Surf Forecast and Surf Report

Issued: 11 pm 17 Sep 2026 (local time)

Forecast update in  hr  min

Today's Avellanas Rivermouth sea temperature is
30.4°C
2.4° 

Avellanas Rivermouth surf forecast is for near shore open water. Breaking waves will often be smaller at less exposed spots.


Avellanas Rivermouth surf forecast from 18 Sep 2026:

  • Best quality surf: Sunday 20 Sep, 6AM (local time) - 2.5ft (0.8m), 19s period, SW swell with glassy winds.
  • Most powerful swell: Monday 21 Sep, 9AM (local time) - 3.5ft (1.1m), 18s period, SW swell with 679 kJ wave energy.
  • Next surfable swell (1★+): Friday 18 Sep, 12PM (local time) - 3ft (0.9m), 13s period with SW swell.

Best Forecast Surf Conditions for Avellanas Rivermouth this week:

The surf forecast for Avellanas Rivermouth over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Friday (Sep 18) at 12PM. The primary swell is predicted to be 0.9m and 13s period with a secondary swell of 0.6m and 8s. The wind is predicted to be glassy as the swell arrives.

The most powerful waves expected at Avellanas Rivermouth in the next 16 days are 1.1m 18s and forecast to arrive on Monday (Sep 21) at 9AM. Winds are predicted to be glassy at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.2m 6s period and expected on Friday (Sep 18) at 3PM.

Wave TypeTime (CST) & Date Wave Height & Period
Next good surf (1 star+)12PM (Fri 18th Sep)3ft (0.9m) 13s
Best Surf 6AM (Sun 20th Sep)2.5ft (0.8m) 19s
Most Powerful 9AM (Mon 21st Sep)3.5ft (1.1m) 18s

Table - best surf conditions forecast for Avellanas Rivermouth over the next 16 days.


Short Range Forecast

Heavy rain (total 26mm), heaviest during Sat night. Warm (max 32°C on Fri morning, min 25°C on Thu night). Wind will be generally light.

Days 5-7 Weather Summary

Heavy rain (total 73mm), heaviest during Tue afternoon. Warm (max 28°C on Mon morning, min 24°C on Sun night). Wind will be generally light.

Friday
18
Saturday
19
Sunday
20
Monday
21
Tuesday
22
Wednesday
23
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
1
0
2
2
1
1
2
3
3
2
3
1
1
1
2
1
1
0
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
SW
14
0.9
SW
13
0.6
SW
20
0.6
SW
19
0.6
SW
19
0.7
SW
13
0.8
SW
18
0.9
SW
19
0.9
SW
19
0.9
SW
18
1.1
SW
18
1
SW
17
0.9
SW
16
1
SW
16
0.9
SW
16
1
SW
16
0.8
SW
15
0.8
SW
15
0.9
SW
15
Wave Graph
Metric surfscale
Energy kJ
317
249
239
236
222
167
396
621
614
516
679
582
443
498
421
480
335
309
355
Wind (km/h)
10
E
20
ENE
15
SW
5
ESE
5
NE
15
SW
5
ESE
5
NNE
15
WSW
10
ENE
5
SE
10
SSE
15
SE
10
SE
10
SSE
15
SSE
10
SE
15
SE
10
SSE
Wind State
on
cross-on
cross-off
glassy
cross-on
cross-off
on
glassy
off
cross-on
glassy
cross-on
cross-on
cross-on
cross
cross
cross-on
cross-on
cross
High Tide
7:08AM2.10m
7:39PM1.83m
7:57AM1.97m
8:36PM1.73m
8:57AM1.87m
9:46PM1.68m
10:07AM1.84m
10:59PM1.73m
11:15AM1.87m
11:59PM1.84m
12:13PM1.95m
00:47AM1.99m
Low Tide
00:52AM0.61m
1:32PM0.60m
1:39AM0.74m
2:27PM0.71m
2:36AM0.85m
3:33PM0.78m
3:48AM0.91m
4:43PM0.78m
5:02AM0.88m
5:44PM0.72m
6:04AM0.79m
6:33PM0.63m
clear
part cloud
part cloud
clear
part cloud
cloud
thunderstorm
part cloud
thunderstorm
thunderstorm
rain showers
thunderstorm
mod rain
mod rain
thunderstorm
thunderstorm
thunderstorm
thunderstorm
rain showers
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
5:31
5:31
5:31
5:31
5:31
5:31
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
5:42
5:40
5:39
5:39
5:38
5:38
 mm
22
4
9
3
13
6
6
18
11
2
5
5
Temp °C
27
32
29
28
30
30
27
30
28
26
28
27
26
27
25
25
27
26
26
Feels °C
30
36
31
32
33
32
31
33
31
30
32
30
28
30
28
28
30
29
30
  • 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 Avellanas Rivermouth Surf forecast

The above surf forecast table for Avellanas Rivermouth provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Avellanas Rivermouth can be found by selecting the local surf guide option on the grey menu. Our Avellanas Rivermouth 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 (Avellanas Rivermouth) 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 Avellanas Rivermouth 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.

Avellanas Rivermouth is 44 km (27 miles) from Nicoya. If you plan a holiday in Guanacaste, look for hotels and other accommodation in Nicoya. Nicoya has rooms for a wide range of budgets as well as car hire and transport links.

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