Surf Forecasts:
Monabe Rivermouth surf forecast from 20 Aug 2026:
- Best quality surf: Tuesday 25 Aug, 6AM (local time) - 15ft (4.5m), 17s period, SSE swell with cross-offshore winds.
- Most powerful swell: Tuesday 25 Aug, 3PM (local time) - 16ft (5.0m), 16s period, SSE swell with 12,971 kJ wave energy.
- Next surfable swell (1★+): Friday 21 Aug, 3AM (local time) - 3.5ft (1.0m), 9s period with S 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 Friday (Aug 21) at 3AM. The primary swell is predicted to be 1.0m and 9s period with a secondary swell of 0.4m and 11s. The wind is predicted to be offshore as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 5.0m 16s and forecast to arrive on Tuesday (Aug 25) 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 1.0m 9s period and expected on Friday (Aug 21) at 6PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3AM (Fri 21st Aug) | 3.5ft (1.0m) 9s |
| Best Surf | 6AM (Tue 25th Aug) | 15ft (4.5m) 17s |
| Most Powerful | 3PM (Tue 25th Aug) | 16ft (5.0m) 16s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s have a look at what’s on the cards for the next couple of weeks.
We’re looking at a very quiet start, with basically nothing doing until Monday the 24th of August. After that, things get real interesting real quick, but you’ll need to be patient and pick your moments.
The first surf worth paddling out for is Monday morning, the 24th of August, at Monabe Rivermouth (river). It’s a very sheltered spot, and it’s one that rarely breaks, so when it’s on, you’ve got to pay attention. The water temp is about average for this time of year, so nothing wild there. That morning we’ve got a 4 ft SE groundswell with a long 18-second period, and the combined energy is moderate (2092). The wind is glassy, light out of the S, so conditions should be clean. This is a good one – expect very good surf.
But the real standout, the one you’ll remember, is Tuesday the 25th of August. Tuesday morning is where it’s at. The swell jumps to a solid 15 ft from the SSE, with a very long 16-second period. The energy is massive (11456) – this is a powerful, deep ocean groundswell. With a glassy NNE breeze, it’s going to be excellent for experienced surfers. That’s a big call, but it’s right there. Tuesday afternoon gets a bit messy with a cross-shore wind picking up, so aim for the early session.
There is a gap after this, with nothing good until the following week. The 31st of August Monday morning brings a clean 6 ft SE swell (13-second period, energy 1191) with glassy conditions – good surf, but not the standout. Then Tuesday the 1st of September morning has a 7 ft ESE swell (14 seconds, energy 2103) and glassy winds – that’s very good surf again.
And then we have a big, promising, but less certain standout for the 3rd of September Thursday morning. It’s a long way out, but the numbers are huge: 16 ft SE swell, 18-second period, energy 16617. If it holds, that’s an excellent, expert-only session with glassy conditions. Definitely one to watch.
Between the 25th and the 3rd, there are a few poor days. The 26th and 27th are blown out with gale-force winds, and the 28th and 29th have small, ordinary surf. The 30th is glassy but only surfable, not special.
So, bottom line: If you’re experienced, the morning of Tuesday the 25th of August is your best bet. The 3rd of September is a promising long-range option. For the rest, pick the glassy mornings with the bigger swells, but don’t expect much from the weekend.
Rusty.
Short Range ForecastMostly dry. Warm (max 29°C on Sat morning, min 25°C on Thu night). Wind will be generally light. | Days 5-7 Weather SummaryHeavy rain (total 234mm), heaviest during Wed afternoon. Warm (max 32°C on Tue afternoon, min 24°C on Mon night). Winds increasing (calm on Tue morning, severe gales from the SE by Wed afternoon). | ||||||||||||||||||
Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | ||||||||||||||
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) | S 9 | S 9 | S 9 | SE 11 | SE 11 | ESE 10 | E 10 | SE 11 | E 10 | SE 15 | SE 18 | SE 17 | SE 17 | SSE 16 | SSE 16 | SSE 14 | S 12 | SSE 10 | SSE 10 |
Wave Graph | |||||||||||||||||||
126 | 171 | 171 | 30 | 33 | 35 | 31 | 35 | 47 | 75 | 1101 | 4438 | 8148 | 11372 | 12971 | 8457 | 2299 | 1956 | 1301 | |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | glassy | on | glassy | glassy | on | glassy | glassy | on | cross-off | glassy | on | off | glassy | cross | cross-off | cross | cross-on | on |
High Tide | 9:56PM1.50m | 2:33PM1.21m | 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 | |||||||
Low Tide | 5:50AM0.67m | 3:45PM1.21m | 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 | |||||||
— | 5:30 | — | — | 5:31 | — | — | 5:31 | — | — | 5:31 | — | — | 5:33 | — | — | 5:33 | — | — | |
6:45 | — | 6:45 | — | — | 6:44 | — | — | 6:42 | — | — | 6:40 | — | — | 6:39 | — | — | 6:38 | — | |
mm | — | — | — | — | — | — | — | — | — | — | — | — | 1 | — | — | 27 | 81 | 125 | 249 |
Temp °C | 26 | 28 | 28 | 26 | 29 | 29 | 26 | 29 | 29 | 26 | 29 | 28 | 26 | 31 | 32 | 28 | 27 | 27 | 27 |
Feels °C | 31 | 32 | 32 | 31 | 33 | 33 | 30 | 32 | 32 | 31 | 33 | 32 | 31 | 32 | 32 | 28 | 22 | 18 | 24 |
Swell 1 Height (m) Direction Period (s) | S 9 | S 9 | S 9 | S 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SE 16 | SE 17 | SE 17 | SSE 16 | SSE 16 | SSE 14 | S 12 | SSE 10 | SSE 10 |
126 | 171 | 171 | 165 | 135 | 103 | 131 | 113 | 86 | 96 | 991 | 4438 | 8148 | 11372 | 12971 | 8457 | 2299 | 1956 | 1301 | |
Swell 2 Height (m) Direction Period (s) | ESE 10 | SE 11 | ESE 11 | SE 11 | E 10 | ESE 10 | E 10 | E 10 | E 10 | SE 15 | SE 18 | S 10 | S 9 | E 12 | E 14 | E 14 | E 13 | E 19 | SSW 11 |
39 | 30 | 44 | 30 | 29 | 35 | 31 | 35 | 47 | 75 | 1101 | 96 | 61 | 44 | 37 | 91 | 85 | 7 | 211 | |
Swell 3 Height (m) Direction Period (s) | ESE 7 | ESE 7 | ESE 7 | E 9 | SE 11 | ESE 10 | ESE 6 | SE 11 | SE 11 | SE 12 | SSW 9 | E 12 | E 12 | E 15 | — | — | E 19 | E 13 | E 12 |
10 | 9 | 9 | 15 | 33 | 10 | 8 | 29 | 29 | 69 | 90 | 145 | 44 | 40 | — | — | 7 | 119 | 72 | |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | E 12 | — | SE 10 | — | — |
— | — | — | — | — | — | — | — | — | — | — | — | — | — | 24 | — | 612 | — | — | |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 9 | 0 | 42 | 9 | 9 | 42 | 9 | 9 | 42 | 9 | 0 | 75 | 0 | 0 | 638 | 387 | 638 | 638 | 230 |
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.











