Surf Forecasts:
Avellanas Rivermouth surf forecast from 2 Sep 2026:
- Best quality surf: Friday 4 Sep, 12AM (local time) - 4.5ft (1.3m), 18s period, SW swell with glassy winds.
- Most powerful swell: Saturday 5 Sep, 9AM (local time) - 6ft (1.8m), 16s period, SW swell with 1,552 kJ wave energy.
- Next surfable swell (1★+): Thursday 3 Sep, 12AM (local time) - 2.5ft (0.8m), 16s 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 Thursday (Sep 03) at 12AM. The primary swell is predicted to be 0.8m and 16s period with a secondary swell of 0.9m and 12s. 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 1.8m 16s and forecast to arrive on Saturday (Sep 05) 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 0.8m 6s period and expected on Monday (Sep 07) at 6PM.
| Wave Type | Time (CST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12AM (Thu 3rd Sep) | 2.5ft (0.8m) 16s |
| Best Surf | 12AM (Fri 4th Sep) | 4.5ft (1.3m) 18s |
| Most Powerful | 9AM (Sat 5th Sep) | 6ft (1.8m) 16s |
Table - best surf conditions forecast for Avellanas Rivermouth over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let's get into it.
We've got a solid stretch of surf coming up at the Rivermouth at Avellanas. The water is sitting at a warm 86°, which is a touch warmer than normal for this time of year, so you can leave the thick rubber at home.
The real standout of this whole forecast is the Saturday morning surf on the 5th of September. The swell is going to be a punchy 6ft from the southwest, and the wind is forecast to be dead glass. That means the river mouth will be looking absolutely pristine. The combined energy of all swells directed here is a solid 1588, which tells you there's plenty of power in the water. That's a morning for the experienced crew to get out there and score some proper waves. For the less experienced, 6ft is starting to push into the bigger range, so be smart.
The Thursday afternoon on the 3rd of September and the Saturday afternoon on the 5th are also worth a mention. The swell is a touch smaller, around 3ft to 5ft, with clean cross-off winds from the southwest. The combined energy readings are high (922 for the 3rd, 1232 for the 5th), so the lines will still have plenty of push. The swell is a long-period groundswell, coming in at 16-19 seconds, which is great for a river mouth setup like this. It'll mean longer lulls between sets, but the waves that do come through will be well-shaped and have plenty of energy.
Later in the week, the 17th of September looks promising again. The Thursday morning has a glassy 3ft swell from the southwest, with a combined energy of 704. That's a beautiful window for a clean, fun session. The afternoons are generally showing clean cross-off winds, which is a pattern that holds for most of the run.
The only real downside is that this break can get crowded, so for the standouts, especially the glassy Saturday morning, expect company. The 4th of September has a solid 5ft in the afternoon, with clean winds and a combined energy of 1650, but it's a bigger afternoon that might be better for the more experienced. The period drops to 17 seconds, which is still good.
Overall, get your eyes on the 5th of September morning and the 17th of September morning. The rest of the run has plenty of clean, ridable days, but those two are the true highlights.
Rusty.
Short Range ForecastLight rain (total 3mm), mostly falling on Thu afternoon. Warm (max 32°C on Thu morning, min 26°C on Wed night). Wind will be generally light. | Days 4-6 Weather SummaryHeavy rain (total 43mm), heaviest during Sat night. Warm (max 31°C on Mon morning, min 26°C on Sat night). Wind will be generally light. | ||||||||||||||||||||
Wednesday 2 | Thursday 3 | Friday 4 | Saturday 5 | Sunday 6 | Monday 7 | Tuesday 8 | |||||||||||||||
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 16 | SW 16 | SW 16 | SW 19 | SW 18 | SW 17 | SW 17 | SW 16 | SW 16 | SW 16 | SW 15 | SW 14 | SW 14 | SW 14 | SW 14 | SW 14 | SW 13 | SW 18 | SW 13 | SW 16 |
Wave Graph  | |||||||||||||||||||||
 kJ | 300 | 326 | 371 | 296 | 577 | 1099 | 1297 | 1519 | 1314 | 1552 | 1164 | 949 | 833 | 833 | 658 | 507 | 410 | 342 | 312 | 224 | 367 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-off | glassy | cross-on | cross-off | glassy | cross-on | cross-off | on | glassy | cross-off | cross-on | cross-on | cross-off | glassy | cross-on | cross-off | glassy | cross-on | on | on |
High Tide | 6:09PM2.19m | 6:30AM2.44m | 6:57PM2.09m | 7:21AM2.34m | 7:53PM1.99m | 8:21AM2.24m | 9:01PM1.92m | 9:32AM2.17m | 10:19PM1.93m | 10:48AM2.17m | 11:35PM2.03m | 12:00PM2.23m | 00:41AM2.19m | ||||||||
Low Tide | 12:04PM0.28m | 00:10AM0.33m | 12:52PM0.35m | 00:59AM0.42m | 1:47PM0.43m | 1:56AM0.52m | 2:52PM0.51m | 3:06AM0.60m | 4:05PM0.53m | 4:25AM0.62m | 5:19PM0.48m | 5:42AM0.56m | 6:24PM0.38m | ||||||||
 | |  | |  | | | |  |  | |  | | | | | | | |  |  | |
 | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — |
 | — | 5:52 | — | — | 5:51 | — | — | 5:50 | — | — | 5:50 | — | — | 5:49 | — | — | 5:49 | — | — | 5:47 | — |
mm | — | — | — | — | 1 | — | — | — | 2 | 1 | 4 | 12 | — | 10 | 4 | — | 11 | 1 | — | — | — |
Temp °C | 31 | 29 | 28 | 32 | 29 | 28 | 30 | 29 | 28 | 29 | 29 | 27 | 29 | 29 | 26 | 31 | 29 | 27 | 33 | 32 | 27 |
Feels °C | 32 | 30 | 32 | 35 | 31 | 32 | 32 | 31 | 32 | 33 | 31 | 31 | 32 | 32 | 31 | 35 | 32 | 31 | 35 | 36 | 28 |
Swell 1 Height (m) Direction Period (s) | SW 13 | SW 13 | SW 16 | SW 16 | SW 19 | SW 18 | SW 17 | SW 17 | SW 16 | SW 16 | SW 16 | SW 15 | SW 14 | SW 14 | SW 14 | SW 14 | SW 14 | SW 13 | SW 13 | SW 13 | SW 16 |
| kJ | 238 | 238 | 371 | 291 | 577 | 1099 | 1297 | 1519 | 1314 | 1552 | 1164 | 949 | 833 | 833 | 658 | 507 | 410 | 342 | 245 | 199 | 367 |
Swell 2 Height (m) Direction Period (s) | SW 18 | SW 16 | SW 12 | SW 12 | SSW 12 | SSW 11 | SSW 11 | SSW 11 | S 11 | WNW 9 | S 7 | S 6 | S 6 | S 6 | S 6 | SSW 6 | WNW 11 | WNW 11 | SW 18 | SW 17 | SW 12 |
| kJ | 300 | 326 | 205 | 144 | 174 | 103 | 103 | 103 | 89 | 26 | 43 | 31 | 20 | 29 | 30 | 43 | 97 | 95 | 312 | 224 | 114 |
Swell 3 Height (m) Direction Period (s) | S 6 | SSW 6 | S 6 | SW 19 | SW 15 | WNW 9 | WNW 9 | WNW 8 | WNW 9 | S 11 | WNW 9 | NW 8 | WNW 11 | WNW 11 | WNW 12 | WNW 11 | S 6 | SW 18 | WNW 11 | WNW 11 | WNW 11 |
| kJ | 25 | 27 | 18 | 296 | 171 | 26 | 25 | 28 | 28 | 10 | 25 | 17 | 45 | 45 | 54 | 102 | 19 | 155 | 93 | 95 | 100 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | SW 6 | — | — | SSW 6 | NNE 4 |
| kJ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 23 | — | — | 18 | 7 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 1 | 68 | 0 | 1 | 201 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 10 | 1 | 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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