Surf Forecasts:
Avellanas Rivermouth surf forecast from 27 Aug 2026:
- Best quality surf: Monday 31 Aug, 3PM (local time) - 3.5ft (1.1m), 13s period, SW swell with cross-offshore winds.
- Most powerful swell: Saturday 29 Aug, 3PM (local time) - 5ft (1.6m), 16s period, SW swell with 1,314 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 0.7m and 7s. 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 1.6m 16s and forecast to arrive on Saturday (Aug 29) at 3PM. Winds are predicted to be cross-shore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 5s period and expected on Thursday (Aug 27) at 9PM.
| Wave Type | Time (CST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12PM (Mon 31st Aug) | 3.5ft (1.1m) 13s |
| Best Surf | 3PM (Mon 31st Aug) | 3.5ft (1.1m) 13s |
| Most Powerful | 3PM (Sat 29th Aug) | 5ft (1.6m) 16s |
Table - best surf conditions forecast for Avellanas Rivermouth over the next 16 days.
The Lowdown
G’day, Rusty here. Let’s talk about Avellanas Rivermouth over the next couple weeks. It’s a sandbar break, always shifting, but when the river mouth lines up, it’s a little slice of heaven. Water temp is about 86°, a touch warmer than normal for the season—nice.
First real chance to wet a line comes Thursday 29th August afternoon. Swell’s 5ft out of the SW, combined energy at 1377—that’s a solid pulse. Wind goes light and cross-shore, just a few tiny wrinkles on the surface. Tides might be a little funny, but it’s the first time you can actually paddle out and catch something.
The next couple days get blown out in the mornings, so pick your times. Monday 31st August arvo shows 4ft SW swell with a 13-second period, light cross-offshore wind keeping things tidy. Not big, but clean enough for a few fun ones.
Now, the one to circle on the calendar—Saturday 5th September afternoon. You’ve got 5ft of clean SW groundswell, a long 16-second period, energy at 1147. Winds swing offshore from the WSW, light and gentle, makin’ those faces smooth as butter. That long-period swell loves a rivermouth—long walls, proper shape. This is for experienced surfers only; 5ft with that kind of period has some punch.
Beyond that, Tuesday 8th September morning goes glassy—dead flat wind, 2ft of SW groundswell with a 19-second period, energy at 579. Tiny but perfect for a longboard. Then Wednesday 9th September arvo: 4ft, 16-second period, energy at 1082, light cross-offshore wind, clean again. Another beauty for the crew that knows what they’re doin’.
Thursday 10th September arvo also delivers clean conditions with offshore WNW winds and 4ft of SW swell. And Friday 11th September arvo goes glassy with 4ft and a 14-second period. Nice way to wrap it up.
So yeah, the first few days are rough—windy and choppy—but from the 29th August you start seein’ clean, long-period SW pulses. The standout is Saturday 5th September arvo without a doubt. After that, there’s regular glassy windows. Crowds are often here, so get there early. This rivermouth is inconsistent, but when it’s on, it’s worth the wait.
Rusty.
Short Range ForecastLight rain (total 6mm), mostly falling on Thu afternoon. Warm (max 33°C on Thu afternoon, min 26°C on Thu night). Winds increasing (light winds from the E on Thu afternoon, fresh winds from the ENE by Fri morning). | Days 4-6 Weather SummaryModerate rain (total 13mm), heaviest on Tue afternoon. Warm (max 33°C on Mon morning, min 25°C on Mon night). Wind will be generally light. | ||||||||||||||||||||
Thursday 27 | Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | Tuesday 1 | Wednesday 2 | |||||||||||||||
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 18 | SW 15 | SW 16 | SW 19 | SW 19 | SW 18 | SW 16 | SW 16 | SW 15 | SW 14 | SW 14 | SW 14 | SW 13 | SW 13 | SW 13 | SW 12 | SW 12 | SW 12 | SW 13 | SW 16 | SW 16 |
Wave Graph  | |||||||||||||||||||||
 kJ | 154 | 106 | 248 | 531 | 358 | 1215 | 1230 | 1314 | 1105 | 911 | 821 | 621 | 451 | 386 | 331 | 301 | 297 | 223 | 246 | 326 | 371 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | on | on | cross-on | on | on | on | cross | on | cross-on | cross | on | cross-on | cross-off | on | on | cross-on | cross-on | cross-off | cross-off | glassy |
High Tide | 2:16PM2.21m | 2:44AM2.22m | 2:55PM2.28m | 3:20AM2.35m | 3:32PM2.33m | 3:54AM2.45m | 4:09PM2.34m | 4:30AM2.51m | 4:47PM2.32m | 5:07AM2.53m | 5:26PM2.27m | 5:46AM2.50m | 6:09PM2.19m | ||||||||
Low Tide | 8:31PM0.38m | 8:48AM0.45m | 9:06PM0.30m | 9:27AM0.36m | 9:40PM0.25m | 10:04AM0.29m | 10:14PM0.23m | 10:42AM0.25m | 10:50PM0.24m | 11:22AM0.24m | 11:28PM0.27m | 12:04PM0.28m | 00:10AM0.33m | ||||||||
 |  |  | | |  | | | |  | | | | | | | | | | | | |
 | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — |
 | — | 5:54 | — | — | 5:54 | — | — | 5:53 | — | — | 5:52 | — | — | 5:52 | — | — | 5:52 | — | — | 5:52 | — |
mm | — | 3 | 2 | — | — | — | — | 1 | — | 1 | 3 | — | — | 2 | — | 1 | 3 | 3 | — | — | 3 |
Temp °C | 32 | 33 | 27 | 33 | 32 | 29 | 32 | 30 | 27 | 32 | 30 | 28 | 33 | 30 | 28 | 29 | 27 | 26 | 29 | 29 | 27 |
Feels °C | 33 | 37 | 30 | 31 | 32 | 27 | 34 | 33 | 28 | 35 | 34 | 31 | 37 | 33 | 30 | 30 | 30 | 29 | 31 | 31 | 31 |
Swell 1 Height (m) Direction Period (s) | S 7 | S 7 | SW 16 | SW 19 | SW 19 | SW 18 | SW 16 | SW 16 | SW 15 | SW 14 | SW 14 | SW 14 | SW 13 | SW 13 | SSW 7 | SW 12 | SW 12 | S 7 | SSW 7 | SW 13 | SW 16 |
| kJ | 56 | 45 | 248 | 531 | 358 | 1215 | 1230 | 1314 | 1105 | 911 | 821 | 621 | 451 | 386 | 102 | 301 | 297 | 157 | 117 | 238 | 371 |
Swell 2 Height (m) Direction Period (s) | SW 15 | N 5 | S 7 | S 7 | SSW 7 | SSE 9 | S 7 | SSW 7 | S 6 | SSW 6 | SSW 6 | SW 6 | S 7 | SSW 7 | SW 13 | SSW 6 | SSW 6 | SW 12 | SW 13 | SW 16 | S 7 |
| kJ | 76 | 16 | 47 | 45 | 35 | 88 | 61 | 63 | 31 | 59 | 47 | 26 | 37 | 105 | 331 | 60 | 53 | 223 | 238 | 326 | 64 |
Swell 3 Height (m) Direction Period (s) | SW 18 | SW 15 | SW 21 | SW 14 | SW 16 | SW 6 | S 11 | — | SW 8 | NNW 15 | NW 15 | S 7 | SW 6 | WNW 10 | W 9 | SW 18 | SW 18 | SW 18 | SW 18 | S 7 | SW 12 |
| kJ | 154 | 106 | 72 | 123 | 125 | 13 | 38 | — | 23 | 21 | 8 | 25 | 19 | 19 | 15 | 84 | 112 | 155 | 246 | 61 | 147 |
Wind waves Height (m) Direction Period (s) | NNE 6 | — | NNE 5 | NNE 6 | — | — | — | — | NNE 5 | — | — | NNE 4 | — | — | — | — | — | S 7 | — | — | — |
| kJ | 18 | — | 13 | 10 | — | — | — | — | 7 | — | — | 4 | — | — | — | — | — | 212 | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 19 | 1 | 1 | 19 | 1 | 1 | 7 | 1 | 1 | 19 | 4 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 321 | 0 |
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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