Surf Forecasts:
Kugenuma Rivermouth surf forecast from 18 Jul 2026:
- Most powerful swell: Thursday 23 Jul, 12AM (local time) - 2.5ft (0.7m), 5s period, SW swell with 28 kJ wave energy.
Best Forecast Surf Conditions for Kugenuma Rivermouth this week:
The most powerful waves expected at Kugenuma Rivermouth in the next 16 days are 0.7m 5s and forecast to arrive on Thursday (Jul 23) at 12AM. Winds are predicted to be glassy at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 2s period and expected on Thursday (Jul 23) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 12AM (Thu 23rd Jul) | 2.5ft (0.7m) 5s |
Table - best surf conditions forecast for Kugenuma Rivermouth over the next 16 days.
The Lowdown
Alright, let’s talk about Kugenuma Rivermouth. It’s been a flat run – not a single decent wave from the 19th through the 26th of July. That’s a solid week of nothing. The wind swung around, the swell was tiny, and honestly, the only thing moving was the occasional ripple. Then things finally wake up.
Come Monday the 27th, the river mouth starts to show some life. The morning brings a 5ft SSE swell with a 14-second period – that’s proper groundswell, and with a gentle offshore breeze from the north, it’s clean. The combined energy sits at 865 (moderate), so there’s some push. Not huge, but for a beginner-friendly spot like this, it’s a fun size. By the afternoon, the swell bumps up to 6ft SSE, period lengthening to 15 seconds, and the wind turns light cross-off from the east. That’s 1,519 units of energy – solid and punchy. This is the best session of the whole window for most surfers.
Tuesday the 28th is the true standout. Morning glass – absolute zero wind from the ESE, and a 8ft SSE swell with a 15-second period. The combined energy is 3,040 (strong), and the waves are groomed, long-period lines. For a river mouth, that’s as good as it gets. The size is right at the top end for intermediates – if you’re confident, you’ll be laughing. The afternoon gets messy though: onshore south wind, 10ft, and the energy jumps to 4,151, but the wind ruins it and the swell is too big for the break to hold shape.
Wednesday the 29th morning is ridiculous – 13ft SSE, 16-second period, glassy, and 7,356 units of energy. That’s heavy, monster swell. The wave comment says wind and tide are favorable, but honestly, it’s too big for this river mouth. Only experts with a death wish and a tow-in setup should even think about it. After that, the swell drops fast and the rest of the week is back to small, messy, and mostly onshore junk.
So bottom line: Monday 27th afternoon and Tuesday 28th morning are your best bets. Tuesday morning is the crown jewel – clean, powerful, and glassy. Don’t sleep on it. After that, it’s back to the waiting game.
– Rusty
Short Range ForecastMostly dry. Warm (max 30°C on Tue morning, min 25°C on Sat night). Wind will be generally light. | Days 5-7 Weather SummaryLight rain (total 3mm), mostly falling on Wed night. Warm (max 31°C on Thu afternoon, min 24°C on Thu night). Wind will be generally light. | ||||||||||||||||||
Sunday 19 | Monday 20 | Tuesday 21 | Wednesday 22 | Thursday 23 | Friday 24 | ||||||||||||||
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 8 | SE 8 | S 3 | S 8 | SSE 9 | SSE 8 | SSW 4 | SW 4 | SSW 4 | SSW 4 | SW 4 | S 3 | SW 5 | SSW 6 | SSE 10 | SE 10 | SSE 9 | SSE 9 | SE 11 |
Wave Graph  | |||||||||||||||||||
 kJ | 10 | 9 | 8 | 5 | 7 | 7 | 10 | 10 | 12 | 14 | 8 | 6 | 28 | 15 | 10 | 15 | 12 | 11 | 18 |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | on | cross-on | on | glassy | on | on | glassy | on | on | glassy | on | glassy | cross-off | glassy | cross-off | cross-off | cross-off | cross-off |
High Tide | 7:12AM1.37m | 8:13PM1.45m | 8:06AM1.27m | 8:44PM1.45m | 9:09AM1.15m | 9:18PM1.42m | 10:39AM1.04m | 9:55PM1.40m | 10:41PM1.37m | 5:19PM1.20m | 11:42PM1.34m | ||||||||
Low Tide | 1:31AM0.73m | 1:34PM0.39m | 2:21AM0.67m | 2:05PM0.55m | 3:19AM0.62m | 2:35PM0.72m | 4:33AM0.58m | 2:58PM0.89m | 6:01AM0.51m | 7:24AM0.41m | 6:26PM1.19m | ||||||||
 |  |  |  | | | | | | | | |  | |  |  | |  | | |
 | — | 4:39 | — | — | 4:41 | — | — | 4:41 | — | — | 4:41 | — | — | 4:43 | — | — | 4:43 | — | — |
 | 6:55 | — | 6:54 | — | — | 6:54 | — | — | 6:53 | — | — | 6:53 | — | — | 6:52 | — | — | 6:52 | — |
mm | — | — | — | — | — | — | — | — | — | — | — | — | 1 | — | 1 | 1 | — | — | 4 |
Temp °C | 26 | 27 | 28 | 27 | 29 | 29 | 29 | 30 | 29 | 29 | 30 | 30 | 29 | 30 | 31 | 26 | 27 | 27 | 25 |
Feels °C | 28 | 28 | 29 | 30 | 32 | 31 | 33 | 33 | 31 | 33 | 35 | 34 | 32 | 32 | 35 | 27 | 28 | 29 | 28 |
Swell 1 Height (m) Direction Period (s) | SE 8 | SE 8 | SSE 7 | SSE 7 | S 3 | SSE 8 | SSE 8 | SSW 4 | SE 8 | S 8 | SSW 4 | SE 7 | SSW 4 | SSW 6 | SSW 6 | SE 10 | SSE 9 | SSE 9 | SE 11 |
| kJ | 10 | 9 | 5 | 5 | 1 | 7 | 7 | 6 | 3 | 1 | 3 | 2 | 10 | 13 | 8 | 15 | 8 | 8 | 18 |
Swell 2 Height (m) Direction Period (s) | S 8 | S 8 | SE 12 | S 8 | SSE 9 | S 7 | S 7 | SSE 8 | SE 11 | SE 11 | SE 8 | SE 11 | SE 11 | SSE 10 | SSE 10 | S 8 | S 7 | SE 7 | SE 16 |
| kJ | 1 | 5 | 6 | 5 | 7 | 1 | 1 | 6 | 5 | 4 | 2 | 5 | 5 | 10 | 10 | 5 | 1 | 2 | 10 |
Swell 3 Height (m) Direction Period (s) | S 8 | E 12 | — | S 10 | S 7 | SE 11 | SE 11 | SE 11 | ESE 11 | — | SE 10 | SE 11 | SE 7 | SE 19 | SE 8 | SE 18 | SE 18 | SE 17 | S 7 |
| kJ | 1 | 3 | — | 2 | 4 | 5 | 5 | 5 | 12 | — | 4 | 4 | 2 | 15 | 3 | 12 | 12 | 11 | 1 |
Wind waves Height (m) Direction Period (s) | SSE 4 | S 3 | S 3 | SSW 4 | SW 3 | SSW 3 | SSW 4 | SW 4 | SSW 4 | SSW 4 | SW 4 | S 3 | SW 5 | NE 2 | — | ESE 4 | — | ESE 4 | — |
| kJ | 4 | 2 | 8 | 4 | 2 | 3 | 10 | 10 | 11 | 14 | 8 | 6 | 28 | 1 | — | 3 | — | 1 | — |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 64 | 85 | 85 | 84 | 84 | 85 | 84 | 84 | 85 | 84 | 84 | 1420 | 84 | 57 | 1433 | 57 | 24 | 24 | 57 |
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.
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