Surf Forecasts:
Avellanas Rivermouth surf forecast from 30 Aug 2026:
- Best quality surf: Friday 4 Sep, 3AM (local time) - 4.5ft (1.3m), 17s period, SW swell with glassy winds.
- Most powerful swell: Friday 4 Sep, 3PM (local time) - 5ft (1.6m), 17s period, SW swell with 1,519 kJ wave energy.
- Next surfable swell (1★+): Monday 31 Aug, 12PM (local time) - 3.5ft (1.1m), 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 Monday (Aug 31) at 12PM. The primary swell is predicted to be 1.1m and 13s period with a secondary swell of 0.4m and 6s. Another secondary swell of 0.3m and 5s is also forecast. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Avellanas Rivermouth in the next 16 days are 1.6m 17s and forecast to arrive on Friday (Sep 04) at 3PM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 6s period and expected on Monday (Aug 31) at 3PM.
| Wave Type | Time (CST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12PM (Mon 31st Aug) | 3.5ft (1.1m) 13s |
| Best Surf | 3AM (Fri 4th Sep) | 4.5ft (1.3m) 17s |
| Most Powerful | 3PM (Fri 4th Sep) | 5ft (1.6m) 17s |
Table - best surf conditions forecast for Avellanas Rivermouth over the next 16 days.
The Lowdown
Alright, let’s get into it for Avellanas Rivermouth. This is a sandbar break that’s fairly consistent and takes swell from the south-west. The water’s sitting at 86°F, which is a touch warmer than normal for this time of year – nothing crazy, but it’s a bit toastier than usual.
Sunday morning starts off with some clouds and a gentle onshore breeze from the ENE at 9 mph, pushing 1.5m of SW swell in with a 14-second period. The combined energy is moderate at 991, but the conditions are a bit marginal. Sunday afternoon is a different story though – the wind swings to a cross-offshore SSW at 9 mph, the swell holds at 1.5m from the SW, and it cleans right up. That’s the pick of the early window.
Monday sees a drop to 1.1m, but the cross-off wind in the afternoon keeps things rideable. Tuesday and Wednesday stay small, around 0.7m to 1.0m, but Wednesday morning is a real standout – glassy conditions with no wind at all, and a long-period 18-second SW swell pushing through. The energy is moderate at 567, and the glassy surface will make it look like a million bucks. That’s a morning to get keen for.
Thursday afternoon is also worth a mention: 0.9m SW swell with a 19-second period, clean offshore wind from the WSW at 9 mph, and combined energy of 730. That’s some proper groundswell running into the river mouth, and it’ll be well-shaped.
Now, the real juice comes in the first week of September. Friday the 4th and Saturday the 5th are the standout days. Friday afternoon delivers 1.6m of SW swell, 17-second period, cross-off wind, and combined energy jumping to 1692 – that’s strong wave energy. Saturday morning is even better: 1.8m SW swell, 16-second period, glassy conditions, and energy at 1574. This is expert-level stuff – over 1.5m, so it’s too big for beginners, and the long period means it’ll be hollow and powerful. For experienced surfers, this is the best on offer.
The following week drops off a bit. Sunday the 6th still has 1.4m SW swell with glassy morning winds, but by Monday the 7th it’s fading to 1.1m. The 9th of September, Wednesday afternoon, sees a bump back up to 1.1m with clean cross-off wind and strong energy of 1056, so that’s another solid session. The 10th and 11th keep the 1–1.3m SW swell running, with clean conditions in the afternoons. After that, the size drops down to 0.6–0.9m through to the 14th, with glassy mornings and clean afternoons, but it’s pretty small.
The absolute standout is Saturday morning, September 5th – 1.8m of SW swell, glassy, long period, and proper power. That’s the one to circle.
Rusty
Short Range ForecastLight rain (total 8mm), mostly falling on Tue night. Warm (max 32°C on Sun morning, min 25°C on Mon night). Wind will be generally light. | Days 4-6 Weather SummaryModerate rain (total 16mm), heaviest on Thu afternoon. Warm (max 29°C on Wed morning, min 26°C on Wed night). Wind will be generally light. | ||||||||||||||||||||
Sunday 30 | Monday 31 | Tuesday 1 | Wednesday 2 | Thursday 3 | Friday 4 | Saturday 5 | |||||||||||||||
AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | |
Swell Height Map |  |  |  |  |  |  |  | ||||||||||||||
Wave Height (m) Direction Period (s) | SW 14 | SW 14 | SW 14 | SW 13 | SW 13 | SW 13 | SW 12 | SW 12 | SW 12 | SW 13 | SW 16 | SW 16 | SW 16 | SW 19 | SW 18 | SW 17 | SW 17 | SW 16 | SW 16 | SW 16 | SW 15 |
Wave Graph  | |||||||||||||||||||||
 kJ | 911 | 899 | 621 | 451 | 444 | 331 | 301 | 297 | 220 | 246 | 326 | 371 | 291 | 577 | 1099 | 1297 | 1519 | 1314 | 1420 | 1179 | 868 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-off | on | cross-on | cross-off | on | on | cross-off | cross-on | glassy | cross-off | cross-on | glassy | cross-off | on | cross-on | cross-off | glassy | on | cross-off | cross-on |
High Tide | 4:09PM2.34m | 4:30AM2.51m | 4:47PM2.32m | 5:07AM2.53m | 5:26PM2.27m | 5:46AM2.50m | 6:09PM2.19m | 6:30AM2.44m | 6:57PM2.09m | 7:21AM2.34m | 7:53PM1.99m | 8:21AM2.24m | 9:01PM1.92m | ||||||||
Low Tide | 10:04AM0.29m | 10:14PM0.23m | 10:42AM0.25m | 10:50PM0.24m | 11:22AM0.24m | 11:28PM0.27m | 12:04PM0.28m | 00:10AM0.33m | 12:52PM0.35m | 00:59AM0.42m | 1:47PM0.43m | 1:56AM0.52m | 2:52PM0.51m | ||||||||
 |  |  | | |  | |  |  | | | |  | | | | | | | |  | |
 | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — |
 | — | 5:52 | — | — | 5:52 | — | — | 5:52 | — | — | 5:52 | — | — | 5:51 | — | — | 5:50 | — | — | 5:50 | — |
mm | — | — | — | — | — | — | — | 1 | 7 | — | 2 | 4 | 1 | 3 | — | 1 | 3 | 2 | 2 | 39 | 7 |
Temp °C | 32 | 29 | 28 | 32 | 30 | 28 | 30 | 29 | 27 | 29 | 28 | 27 | 29 | 29 | 28 | 29 | 29 | 28 | 29 | 28 | 25 |
Feels °C | 37 | 31 | 31 | 35 | 32 | 30 | 31 | 30 | 30 | 33 | 30 | 30 | 34 | 32 | 32 | 31 | 32 | 33 | 32 | 32 | 29 |
Swell 1 Height (m) Direction Period (s) | SW 14 | SW 14 | SW 14 | SW 13 | SW 13 | SW 13 | SW 12 | SW 12 | SW 12 | SW 13 | SW 13 | SW 16 | SW 16 | SW 19 | SW 18 | SW 17 | SW 17 | SW 16 | SW 16 | SW 16 | SW 15 |
| kJ | 911 | 899 | 621 | 451 | 444 | 331 | 301 | 297 | 220 | 238 | 238 | 371 | 291 | 577 | 1099 | 1297 | 1519 | 1314 | 1420 | 1179 | 868 |
Swell 2 Height (m) Direction Period (s) | S 10 | S 10 | S 8 | S 6 | SSW 6 | S 6 | S 7 | SW 18 | S 6 | SW 18 | SW 16 | SSW 12 | SW 12 | SSW 7 | S 7 | SSW 11 | SSW 11 | S 11 | S 11 | S 7 | SSW 7 |
| kJ | 71 | 46 | 31 | 12 | 12 | 20 | 45 | 112 | 38 | 246 | 326 | 180 | 144 | 49 | 33 | 183 | 103 | 89 | 60 | 35 | 71 |
Swell 3 Height (m) Direction Period (s) | SW 6 | N 4 | WSW 6 | WSW 6 | N 4 | W 9 | SW 18 | W 8 | SW 6 | S 6 | SSW 6 | S 6 | SSW 7 | SW 12 | SW 11 | WNW 9 | WNW 9 | WNW 9 | WNW 9 | WNW 9 | WNW 8 |
| kJ | 9 | 3 | 3 | 3 | 5 | 15 | 84 | 6 | 30 | 29 | 32 | 31 | 49 | 112 | 58 | 26 | 25 | 27 | 32 | 31 | 28 |
Wind waves Height (m) Direction Period (s) | — | SW 6 | — | — | SSW 6 | NE 4 | — | S 6 | — | — | — | — | — | — | — | — | — | — | — | — | — |
| kJ | — | 9 | — | — | 23 | 4 | — | 84 | — | — | — | — | — | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 4 | 64 | 1 | 1 | 0 | 1 | 1 | 103 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 |
Best forecast wave conditions in Guanacaste | |||||||||||||||||||||
Best forecast wave conditions in Costa Rica | |||||||||||||||||||||
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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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