Surf Forecasts:
Monabe Rivermouth surf forecast from 21 Aug 2026:
- Best quality surf: Monday 24 Aug, 6PM (local time) - 8ft (2.5m), 17s period, SE swell with glassy winds.
- Most powerful swell: Tuesday 25 Aug, 12PM (local time) - 13ft (4.0m), 16s period, SSE swell with 8,376 kJ wave energy.
- Next surfable swell (1★+): Monday 24 Aug, 6AM (local time) - 2ft (0.6m), 21s period with SE swell.
Best Forecast Surf Conditions for Monabe Rivermouth this week:
The surf forecast for Monabe Rivermouth over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Monday (Aug 24) at 6AM. The primary swell is predicted to be 0.6m and 21s period with a secondary swell of 0.7m and 13s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 4.0m 16s and forecast to arrive on Tuesday (Aug 25) at 12PM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 2.4m 11s period and expected on Wednesday (Aug 26) at 9PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6AM (Mon 24th Aug) | 2ft (0.6m) 21s |
| Best Surf | 6PM (Mon 24th Aug) | 8ft (2.5m) 17s |
| Most Powerful | 12PM (Tue 25th Aug) | 13ft (4.0m) 16s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
G'day, Rusty here. We're looking at a 16-day stretch for Monabe Rivermouth, and I gotta be straight with you—this break is a tricky one. It's a rivermouth setup that rarely breaks, so when it does, it’s a bit of an event. We’ve got a long quiet spell to start, with next to nothing on offer until Monday the 24th of August. Even then, it's marginal at best. The real action doesn't kick off until the following week.
The water temp is sitting about average for this time of year.
Alright, let's get into it. The first real standout is the morning of Tuesday the 25th of August. That’s the one you want to circle. We’ve got a 13ft swell from the SSE with a period of 16 seconds—that’s a proper groundswell with some serious legs on it. The energy is pumping at 8113, so you’re getting strong, powerful waves. The wind is glassy out of the south at 3 mph, meaning the surface will be clean as a whistle. Now, this swell is big, well over 8ft, so it's strictly for experienced surfers only. The long period (16 seconds) will make it a bit straight on a beach break, but at a rivermouth, it could line up nicely and give you some long, racy walls. Keep in mind, this spot is rarely breaking, so if it's on, it'll be special. Crowds are possible here, so get in early.
Tuesday the 1st of September morning is another cracker. We’ve got a 12ft swell from the ESE, period 11 seconds, and energy at 5438. It’s glassy calm with the wind out of the SE at 0 mph, so the waves will be clean and inviting. Again, that’s expert-only territory at over 8ft, but the consistency should be decent with a groundswell.
Then Wednesday the 2nd of September morning has a 13ft swell from the E, period 11 seconds, and energy at 7368. Glassy conditions again (W at 0 mph), making for another high-quality session for the crew in the know.
Thursday the 3rd of September morning also looks solid: 15ft swell from the SSE, period 10 seconds, with a cross-off wind from the NNW at 6 mph, keeping things clean. That’s another one for experts.
Now, be aware there’s a gap with no real recommendations from Thursday afternoon the 3rd of September through to the end of the window, with just ordinary, surfable waves but nothing to write home about.
If I had to pick one absolute standout, it’s Tuesday the 25th of August morning. That combo of a massive, long-period groundswell and glassy conditions at a rarely-breaking rivermouth is as good as it gets here—but keep it between us.
Rusty.
Short Range ForecastMostly dry. Warm (max 29°C on Sat morning, min 25°C on Fri night). Wind will be generally light. | Days 5-7 Weather SummaryHeavy rain (total 98mm), heaviest during Wed night. Warm (max 30°C on Tue morning, min 24°C on Wed night). Wind will be generally light. | ||||||||||||||||||
Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | Thursday 27 | ||||||||||||||
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) | SE 11 | SE 11 | ESE 10 | ESE 14 | E 10 | E 10 | SE 12 | SE 19 | SE 17 | SE 16 | SSE 16 | SSE 15 | SSE 14 | S 13 | S 12 | S 11 | S 9 | S 8 | S 9 |
Wave Graph | |||||||||||||||||||
30 | 33 | 33 | 36 | 35 | 47 | 93 | 738 | 2621 | 3369 | 8030 | 7910 | 6835 | 4415 | 3068 | 1608 | 775 | 512 | 554 | |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | glassy | on | glassy | glassy | on | glassy | on | on | glassy | glassy | cross-on | cross-off | cross | cross-on | cross | cross-on | cross-off | cross-off |
High Tide | 10:41PM1.41m | 4:35PM1.33m | 00:46AM1.36m | 4:50PM1.43m | 2:38AM1.41m | 5:10PM1.53m | 3:40AM1.52m | 5:30PM1.61m | 4:25AM1.63m | 5:51PM1.69m | 5:03AM1.74m | 6:12PM1.76m | |||||||
Low Tide | 7:39AM0.66m | 8:21PM1.28m | 9:06AM0.57m | 9:54PM1.19m | 9:59AM0.46m | 10:30PM1.08m | 10:37AM0.35m | 10:58PM0.96m | 11:10AM0.25m | 11:25PM0.84m | 11:40AM0.20m | 11:53PM0.72m | |||||||
— | 5:31 | — | — | 5:31 | — | — | 5:31 | — | — | 5:33 | — | — | 5:33 | — | — | 5:33 | — | — | |
6:45 | — | 6:44 | — | — | 6:42 | — | — | 6:40 | — | — | 6:39 | — | — | 6:38 | — | — | 6:37 | — | |
mm | — | — | — | — | — | — | — | — | — | — | — | 2 | 4 | 10 | 19 | 52 | 9 | 2 | 6 |
Temp °C | 27 | 29 | 29 | 26 | 29 | 29 | 27 | 29 | 28 | 26 | 30 | 30 | 27 | 28 | 26 | 26 | 25 | 25 | 25 |
Feels °C | 33 | 32 | 32 | 31 | 32 | 31 | 33 | 33 | 31 | 31 | 32 | 32 | 31 | 31 | 28 | 28 | 28 | 28 | 28 |
Swell 1 Height (m) Direction Period (s) | S 9 | SSW 9 | SSW 9 | SSW 8 | SSW 8 | SSW 8 | SSW 8 | SE 19 | SE 17 | SE 16 | SSE 16 | SSE 15 | SSE 14 | S 13 | S 12 | S 11 | S 9 | S 8 | S 9 |
165 | 135 | 103 | 72 | 78 | 48 | 82 | 738 | 2621 | 3369 | 8030 | 7910 | 6835 | 4415 | 3068 | 1608 | 775 | 512 | 554 | |
Swell 2 Height (m) Direction Period (s) | SE 11 | E 10 | ESE 10 | E 10 | E 10 | E 10 | SE 12 | SE 13 | SSW 9 | SSE 18 | E 12 | E 14 | E 14 | E 13 | E 13 | E 12 | E 12 | E 12 | E 11 |
30 | 29 | 33 | 31 | 35 | 47 | 93 | 224 | 48 | 2430 | 44 | 103 | 91 | 85 | 82 | 73 | 44 | 43 | 38 | |
Swell 3 Height (m) Direction Period (s) | E 9 | SE 11 | SE 10 | ESE 14 | SE 10 | SSW 8 | E 12 | SSW 9 | E 12 | S 10 | E 15 | — | — | E 13 | E 19 | E 18 | E 16 | E 15 | E 14 |
15 | 33 | 17 | 36 | 27 | 23 | 47 | 59 | 75 | 46 | 39 | — | — | 84 | 7 | 6 | 20 | 17 | 37 | |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | SE 9 | ESE 9 | — | SSE 8 | — | — |
— | — | — | — | — | — | — | — | — | — | — | — | — | 456 | 486 | — | 475 | — | — | |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 9 | 9 | 42 | 9 | 9 | 42 | 9 | 9 | 50 | 0 | 0 | 75 | 0 | 425 | 50 | 20 | 20 | 0 | 0 |
Best forecast wave conditions in Shikoku | |||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||
Header Global | |||||||||||||||||||
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Information about the Monabe Rivermouth Surf forecast
The above surf forecast table for Monabe Rivermouth provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Monabe Rivermouth can be found by selecting the local surf guide option on the grey menu. Our Monabe 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 (Monabe 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 Monabe 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.
Monabe Rivermouth is 11 km (7 miles) from the city of Aki. If you plan a holiday in Shikoku, look for hotels and other accommodation in Aki. Aki has rooms for a wide range of budgets as well as car hire and transport links.











