Surf Forecasts:
Kugenuma Rivermouth surf forecast from 25 Aug 2026:
- Best quality surf: Thursday 27 Aug, 9AM (local time) - 3.5ft (1.0m), 6s period, SSW swell with offshore winds.
- Most powerful swell: Tuesday 1 Sep, 9PM (local time) - 4.5ft (1.3m), 14s period, S swell with 694 kJ wave energy.
- Next surfable swell (1★+): Thursday 27 Aug, 9AM (local time) - 3.5ft (1.0m), 6s period with SSW swell.
Best Forecast Surf Conditions for Kugenuma Rivermouth this week:
The surf forecast for Kugenuma Rivermouth over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Thursday (Aug 27) at 9AM. The primary swell is predicted to be 1.0m and 6s period with a secondary swell of 0.6m and 6s. Another secondary swell of 0.4m and 9s is also forecast. The wind is predicted to be offshore as the swell arrives.
The most powerful waves expected at Kugenuma Rivermouth in the next 16 days are 1.3m 14s and forecast to arrive on Tuesday (Sep 01) at 9PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.3m 3s period and expected on Thursday (Aug 27) at 3PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9AM (Thu 27th Aug) | 3.5ft (1.0m) 6s |
| Best Surf | 9AM (Thu 27th Aug) | 3.5ft (1.0m) 6s |
| Most Powerful | 9PM (Tue 1st Sep) | 4.5ft (1.3m) 14s |
Table - best surf conditions forecast for Kugenuma Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here, let's talk about what's on the cards for the Kugenuma Rivermouth stretch.
We're looking at a pretty mixed bag over the next 16 days. There's a bit of a slow start, but the real standout is going to be a big, powerful swell that shows up way down the track. The water temp is feeling about average for this time of year, so nothing out of the ordinary there.
The first real action worth paddling out for is a brief window on Wednesday morning, the 26th of August. The wind is glassy, almost dead calm, with a clean 3ft SSW groundswell rolling in at 12 seconds. The combined energy is at a moderate 250, and it’s going to feel clean and fun. But don't get too excited, because that afternoon the wind swings onshore from the SSW and it gets messy fast.
We then hit a flat spell. From Thursday the 27th right through to the end of the month, the swell drops off. There are a few mornings with glassy or offshore winds, but the waves are tiny, barely 1.0ft to 1ft, with weak energy readings in the low 20s to 30s. It's basically a lake out there. Not worth dragging the board out.
Monday the 31st of August and Tuesday the 1st of September see a little pulse of energy come back. The morning of the 1st is the pick of this period, with a 3ft SSW swell (combined energy 250) and a steady offshore NNE breeze at 15 km/h. The afternoon even bumps up to 3ft from the S with a clean cross-off breeze. It's not huge, but it's clean and surfable, and the crowds are often around here, so expect some company.
The middle of the first week of September, from the 2nd to the 4th, gets blown out. The swell actually builds, hitting 5ft to 7ft on the 2nd, with some serious energy (2559 on Wednesday afternoon), but the wind is howling onshore from the SSW and S at 20 to 40 km/h. It's a complete mess – that's kite-surfing territory, not for paddling.
After a few more days of small, clean but weak surf, we get to the big one. Mark your calendars for Tuesday morning, the 8th of September. This is the standout. The forecast is showing an 12ft swell from the S, with an incredible combined energy of 3172. The wind is a moderate offshore from the NE at 20 km/h, keeping it clean. Now, a word of caution: this is a big swell. At 12ft, this is strictly for experienced surfers, and the period is 12 seconds, so it's a proper groundswell that will really jack up on the river mouth. It might be too big for the break, but if you're an expert, this is the day to chase. The Tuesday afternoon also looks solid at 12ft with a clean cross-off breeze.
The swell drops back through the 9th and 10th, but there's still some decent, clean swell in the 5ft to 7ft range on the Wednesday morning (9th Sept) with a moderate offshore wind. That's a good backup option for the experienced crew.
So, to wrap it up: the first week is mostly a bust with a few clean but small windows. The real, powerful groundswell hits on the 8th of September, but it's big and for experts only. The morning of the 1st of September offers the best chance for a clean, manageable session for the average surfer.
Rusty.
Short Range ForecastHeavy rain (total 24mm), heaviest during Thu morning. Warm (max 31°C on Wed afternoon, min 24°C on Thu afternoon). Wind will be generally light. | Days 4-6 Weather SummaryLight rain (total 4mm), mostly falling on Sat morning. Warm (max 26°C on Mon morning, min 23°C on Sat morning). Wind will be generally light. | ||||||||||||||||||||
Wednesday 26 | Thursday 27 | Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | Tuesday 1 | |||||||||||||||
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) | SSW 12 | SSW 12 | SSW 11 | SSW 6 | S 11 | S 10 | S 9 | SSW 8 | SSW 6 | SSW 8 | SSE 11 | SSW 8 | SSW 8 | SSE 10 | SSW 7 | S 12 | SSW 11 | SSW 10 | SSW 19 | S 16 | S 13 |
Wave Graph | |||||||||||||||||||||
183 | 137 | 68 | 63 | 55 | 45 | 57 | 76 | 18 | 19 | 12 | 11 | 11 | 10 | 10 | 12 | 25 | 35 | 69 | 612 | 600 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | on | cross-on | off | off | on | on | cross-on | off | cross-off | off | off | off | off | off | off | cross-on | cross-on | cross-on | on | on |
High Tide | 5:16PM1.46m | 4:04AM1.47m | 5:28PM1.47m | 4:44AM1.53m | 5:42PM1.49m | 5:22AM1.55m | 5:58PM1.52m | 6:00AM1.54m | 6:18PM1.55m | 6:40AM1.50m | 6:40PM1.58m | 7:22AM1.41m | 7:05PM1.57m | ||||||||
Low Tide | 10:23AM0.25m | 10:42PM0.89m | 10:52AM0.27m | 11:05PM0.77m | 11:19AM0.31m | 11:29PM0.65m | 11:43AM0.38m | 11:57PM0.54m | 12:07PM0.47m | 00:28AM0.45m | 12:30PM0.58m | 1:04AM0.40m | 12:53PM0.70m | 1:45AM0.39m | |||||||
5:09 | — | — | 5:09 | — | — | 5:09 | — | — | 5:11 | — | — | 5:11 | — | — | 5:11 | — | — | 5:13 | — | — | |
— | 6:17 | — | — | 6:16 | — | — | 6:15 | — | — | 6:14 | — | — | 6:13 | — | — | 6:10 | — | — | 6:09 | — | |
mm | — | — | 4 | 9 | 2 | 4 | 1 | — | 4 | 2 | — | 1 | 1 | — | — | — | — | — | — | — | 4 |
Temp °C | 29 | 31 | 29 | 26 | 25 | 25 | 27 | 28 | 28 | 24 | 24 | 24 | 24 | 25 | 25 | 26 | 26 | 26 | 27 | 28 | 27 |
Feels °C | 33 | 33 | 31 | 28 | 26 | 26 | 28 | 30 | 33 | 25 | 24 | 24 | 25 | 27 | 28 | 29 | 29 | 29 | 29 | 29 | 30 |
Swell 1 Height (m) Direction Period (s) | SSW 12 | SSW 12 | SSW 11 | S 6 | S 6 | S 10 | S 9 | SSE 10 | SSW 6 | SSW 8 | SSW 7 | SSW 8 | SSW 8 | SSW 8 | SSW 7 | S 7 | SSW 11 | SSW 10 | S 10 | S 16 | S 13 |
183 | 137 | 68 | 23 | 18 | 45 | 57 | 9 | 18 | 19 | 11 | 11 | 11 | 6 | 10 | 4 | 25 | 35 | 44 | 612 | 600 | |
Swell 2 Height (m) Direction Period (s) | S 9 | SSE 9 | SSE 9 | SSE 9 | S 11 | SSE 10 | SSE 9 | SW 9 | S 8 | SSE 11 | SSE 11 | SSE 10 | SSE 10 | SSE 10 | SSE 10 | S 12 | SSW 8 | SSE 10 | SSW 19 | E 10 | E 10 |
83 | 49 | 31 | 28 | 55 | 9 | 8 | 3 | 12 | 11 | 12 | 10 | 10 | 10 | 10 | 12 | 7 | 9 | 69 | 2 | 2 | |
Swell 3 Height (m) Direction Period (s) | E 12 | E 12 | S 10 | SW 10 | SSE 10 | SSW 10 | SW 9 | SE 15 | SSE 10 | — | SSW 8 | E 6 | ESE 5 | — | S 12 | SSE 10 | SSE 9 | S 12 | SE 10 | SE 10 | SE 10 |
3 | 3 | 19 | 25 | 18 | 9 | 3 | 8 | 9 | — | 6 | 1 | 2 | — | 3 | 9 | 9 | 12 | 4 | 15 | 15 | |
Wind waves Height (m) Direction Period (s) | SW 4 | SSW 5 | SSW 5 | SSW 6 | NE 3 | SSW 6 | — | SSW 8 | — | — | NE 2 | — | — | NNE 2 | — | — | — | SSW 2 | S 3 | — | — |
11 | 30 | 40 | 63 | 1 | 10 | — | 76 | — | — | 1 | — | — | 1 | — | — | — | 1 | 1 | — | — | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 7 | 7 | 7 | 0 | 0 | 84 | 84 | 4 | 24 | 57 | 57 | 69 | 24 | 61 | 61 | 24 | 24 | 30 | 18 | 64 | 7 |
Best forecast wave conditions in Kanagawa | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
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Information about the Kugenuma Rivermouth Surf forecast
The above surf forecast table for Kugenuma Rivermouth provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Kugenuma Rivermouth can be found by selecting the local surf guide option on the grey menu. Our Kugenuma 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 (Kugenuma 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 Kugenuma 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.











