
Surf Forecasts:
Kugenuma Rivermouth surf forecast from 15 Sep 2026:
- Best quality surf: Monday 21 Sep, 3PM (local time) - 10ft (3.0m), 14s period, SSE swell with offshore winds.
- Most powerful swell: Monday 21 Sep, 3PM (local time) - 10ft (3.0m), 14s period, SSE swell with 3,826 kJ wave energy.
- Next surfable swell (1★+): Tuesday 15 Sep, 9PM (local time) - 2.5ft (0.7m), 6s period with SSE 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 Tuesday (Sep 15) at 9PM. The primary swell is predicted to be 0.7m and 6s period with a secondary swell of 0.4m and 6s. 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 3.0m 14s and forecast to arrive on Monday (Sep 21) at 3PM. Winds are predicted to be offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.7m 5s period and expected on Monday (Sep 21) at 3PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Tue 15th Sep) | 2.5ft (0.7m) 6s |
| Best Surf | 3PM (Mon 21st Sep) | 10ft (3.0m) 14s |
| Most Powerful | 3PM (Mon 21st Sep) | 10ft (3.0m) 14s |
Table - best surf conditions forecast for Kugenuma Rivermouth over the next 16 days.
The Lowdown
Alright, let’s break it down.
For the next two weeks, there’s a lot of nothing on the menu, but there’s one real standout sitting about a week out that you need to know about. Beyond that, it’s small, weak stuff for the most part.
Right now, Kugenuma Rivermouth (Japan) is flat. I’m talking 0.3ft to 1ft at best, with a bit of longer-period energy but no size to it. The wind is offshore a lot of the time, which is nice, but there’s just nothing to ride. The swell energy is minimal – single digits to the low 20s – so it’s not even a case of trying to squeeze something out of it. The water is a touch warmer than normal at 81°, but that doesn’t change the fact you’d be floating.
We’re looking at a long dry spell from now through the 18th. Several days of nothing. If you head out, it’ll be for a paddle, not a surf.
Then on the 19th and 20th, we get a bit of life. The swell pushes up to around 4ft to 4ft from the southeast with a period stretching to 12 or 13 seconds. Energy jumps into the 400s – that’s moderate – but the wave call is still marginal. The wind is fresh offshore, so it’s clean but a bit lumpy and not really organised. Still not the day.
But the 21st is the one. That Monday morning starts at around 8ft from the SSE at 13 seconds, with energy over 2000. Then the afternoon is where it turns on: 10ft, SSE, 14 seconds, and energy almost at 3800. That’s proper, solid swell. The wind is moderate offshore out of the NNE, and the call is excellent for experienced surfers. This is big, powerful, and clean. At 10ft, this is expert-only territory. Kugenuma Rivermouth is going to have serious lines on it. This is the standout, no question.
After that, it drops off fast. The 22nd is back to 2ft, and the 23rd is a washout with a strong southwest gale – 70 km/h – and heavy rain. The 24th through the 27th are mostly poor, tiny surf in the 0.5ft to 1ft range. The 28th tries to mix in some short-period slop, but it’s not happening.
The last couple of days, the 29th and 30th, offer a little something. The 29th afternoon you’ve got about 3ft at 11 seconds from the SSE with light cross-offshore wind, and the call is good conditions. The 30th morning is similar – around 3ft, 10 seconds, light offshore, clean. These are small but clean days. Perfect for the less experienced crew. The energy is in the low 200s – moderate – but it’s not weak. It’s just clean, rideable, manageable.
So, bottom line: the 21st afternoon is the one to circle. That’s your big day. The 29th and 30th are your clean, smaller fallback. Everything else is mostly a lot of waiting and watching.
Keep an eye on that 21st – 10ft, SSE, 14 seconds, offshore. That’s the one.
Rusty.
Short Range ForecastHeavy rain (total 68mm), heaviest during Wed night. Warm (max 26°C on Tue afternoon, min 18°C on Thu night). Winds increasing (calm on Tue afternoon, fresh winds from the NNE by Thu night). | Days 5-7 Weather SummaryHeavy rain (total 133mm), heaviest during Sat night. Warm (max 24°C on Mon morning, min 19°C on Fri night). Mainly strong winds. | |||||||||||||||||||
Tue 15 | Wednesday 16 | Thursday 17 | Friday 18 | Saturday 19 | Sunday 20 | Monday 21 | ||||||||||||||
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) | SSE 7 | S 6 | SE 7 | SE 8 | SE 8 | SSE 8 | SSE 9 | E 11 | S 12 | SE 16 | SE 14 | SE 13 | SE 12 | SE 12 | SSE 12 | SSE 12 | SSE 14 | SSE 13 | SSE 14 | SE 11 |
Wave Graph | ||||||||||||||||||||
42 | 35 | 12 | 17 | 17 | 7 | 8 | 9 | 6 | 39 | 513 | 431 | 437 | 494 | 488 | 441 | 1403 | 2168 | 3826 | 147 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | off | off | off | off | off | off | off | off | off | off | off | off | off | off | off | off | off | off | off |
High Tide | 6:27PM1.60m | 7:41AM1.37m | 6:53PM1.58m | 8:36AM1.26m | 7:20PM1.53m | 9:56AM1.15m | 7:47PM1.45m | 8:14PM1.35m | 4:05PM1.31m | 9:47PM1.23m | 3:49PM1.37m | 1:05AM1.21m | ||||||||
Low Tide | 1:08AM0.31m | 12:46PM0.84m | 1:50AM0.34m | 1:04PM0.96m | 2:44AM0.40m | 1:07PM1.07m | 4:02AM0.48m | 6:00AM0.52m | 8:47PM1.23m | 7:36AM0.48m | 9:09PM1.09m | |||||||||
— | — | 5:24 | — | — | 5:24 | — | — | 5:26 | — | — | 5:26 | — | — | 5:26 | — | — | 5:28 | — | — | |
5:50 | — | — | 5:49 | — | — | 5:46 | — | — | 5:45 | — | — | 5:44 | — | — | 5:43 | — | — | 5:40 | — | |
mm | 3 | 6 | 7 | 7 | 45 | — | — | — | — | — | — | — | 3 | 110 | 17 | 3 | — | — | — | 3 |
Temp °C | 26 | 24 | 22 | 22 | 21 | 21 | 22 | 20 | 21 | 22 | 21 | 20 | 20 | 20 | 21 | 22 | 22 | 24 | 25 | 23 |
Feels °C | 28 | 25 | 23 | 22 | 20 | 17 | 16 | 14 | 15 | 17 | 16 | 15 | 15 | 16 | 19 | 20 | 20 | 23 | 25 | 23 |
Swell 1 Height (m) Direction Period (s) | — | S 6 | SE 7 | SE 8 | SE 8 | SSE 8 | SSE 9 | SE 9 | SE 9 | SE 16 | SE 14 | SE 13 | SE 12 | SE 12 | SSE 12 | SSE 12 | SSE 14 | SSE 13 | SSE 14 | SE 11 |
— | 35 | 12 | 17 | 17 | 7 | 8 | 3 | 3 | 39 | 513 | 431 | 437 | 494 | 488 | 441 | 1403 | 2168 | 3826 | 147 | |
Swell 2 Height (m) Direction Period (s) | E 12 | SSW 6 | SSW 6 | SSW 6 | S 5 | SE 7 | SE 7 | E 11 | S 12 | SE 9 | E 10 | S 10 | S 10 | SSE 14 | — | E 13 | — | — | — | N 5 |
11 | 20 | 7 | 3 | 1 | 2 | 2 | 9 | 3 | 3 | 31 | 2 | 2 | 419 | — | 3 | — | — | — | 4 | |
Swell 3 Height (m) Direction Period (s) | E 14 | E 13 | S 9 | SSW 6 | — | E 12 | SE 9 | SE 9 | SE 12 | SE 12 | — | — | — | — | — | — | — | — | — | SW 7 |
16 | 13 | 2 | 3 | — | 3 | 3 | 3 | 6 | 5 | — | — | — | — | — | — | — | — | — | 2 | |
Wind waves Height (m) Direction Period (s) | SSE 7 | — | NE 3 | NE 2 | NE 3 | NNE 4 | NE 4 | NNE 4 | NNE 4 | NNE 4 | NNE 4 | NNE 4 | NNE 4 | N 4 | NNE 4 | NNE 4 | NNE 4 | N 4 | N 5 | — |
42 | — | 2 | 1 | 5 | 11 | 21 | 21 | 19 | 16 | 15 | 19 | 15 | 13 | 14 | 15 | 24 | 66 | 164 | — | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 7 | 0 | 57 | 57 | 63 | 140 | 545 | 463 | 480 | 222 | 463 | 222 | 222 | 130 | 49 | 69 | 0 | 545 | 0 | 0 |
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.










