Surf Forecasts:
Kugenuma Rivermouth surf forecast from 8 Sep 2026:
- Best quality surf: Thursday 10 Sep, 6AM (local time) - 3.5ft (1.0m), 9s period, S swell with offshore winds.
- Most powerful swell: Wednesday 9 Sep, 9AM (local time) - 6ft (1.9m), 8s period, SSW swell with 509 kJ wave energy.
- Next surfable swell (1★+): Thursday 10 Sep, 6AM (local time) - 3.5ft (1.0m), 9s period with S 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 (Sep 10) at 6AM. The primary swell is predicted to be 1.0m and 9s period with a secondary swell of 0.2m and 11s. 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 1.9m 8s and forecast to arrive on Wednesday (Sep 09) at 9AM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.7m 4s period and expected on Thursday (Sep 10) at 12AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6AM (Thu 10th Sep) | 3.5ft (1.0m) 9s |
| Best Surf | 6AM (Thu 10th Sep) | 3.5ft (1.0m) 9s |
| Most Powerful | 9AM (Wed 9th Sep) | 6ft (1.9m) 8s |
Table - best surf conditions forecast for Kugenuma Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty again.
Looking at the next couple of weeks around Kugenuma, it's mostly a bust. From Tuesday 8th all the way to the morning of Saturday 20th, there’s practically nothing worth paddling out for. A few tiny waves here and there but it's mostly windblown or too weak to be fun. Water temp is roughly 83°F, a touch warmer than what’s normal for this time of year, so at least you won’t be shivering while you’re waiting for nothing.
Kugenuma Rivermouth wakes up on the morning of September 20th. That’s your first real window. Swell is 4ft from the south with a very long 19-second period, combined energy of 876 (moderate). That period means real groundswell power and on a river mouth it’ll bend in nicely. Wind is light offshore from the NNE at 6 mph, clean. Afternoon shows 5ft with 18 seconds but cross-shore wind, so still chunky but with a bit of ripple.
The standout of the whole run is the morning of Monday 22nd September. Swell reaches 6ft from the SE at 16 seconds, combined energy 1891 (strong). Wind is a gentle offshore from the NE at 9 mph, dead clean. That’s proper surf—bigger than 5ft so for experienced surfers only. Long-period groundswell like that will hold up and push nicely through the river mouth. Crowds are likely here often. The afternoon glass-off drops to 3ft with 14 seconds – perfect for cruising.
September 21st morning is the biggest pulse: 8ft from the SSE at 18 seconds, combined energy 3553 (very strong). But north wind ripping at 28 mph offshore makes it a chore to get out. Honestly, that one’s edging into kite-surf territory for strength.
So bottom line: Saturday 20th morning and Monday 22nd morning are the gems. The rest is a long quiet spell.
Rusty.
Short Range ForecastHeavy rain (total 32mm), heaviest during Thu night. Warm (max 29°C on Wed morning, min 18°C on Thu night). Winds increasing (light winds from the S on Tue morning, fresh winds from the NNE by Wed night). | Days 4-6 Weather SummaryLight rain (total 6mm), mostly falling on Fri morning. Warm (max 27°C on Sun afternoon, min 19°C on Fri morning). Wind will be generally light. | ||||||||||||||||||||
Tuesday 8 | Wednesday 9 | Thursday 10 | Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | |||||||||||||||
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) | S 9 | S 9 | SSW 10 | SSW 8 | S 9 | S 9 | S 9 | S 8 | S 8 | S 8 | S 8 | S 7 | S 7 | SSW 7 | SSW 7 | SE 9 | SE 9 | SE 8 | SE 9 | SE 9 | SE 8 |
Wave Graph  | |||||||||||||||||||||
 kJ | 276 | 276 | 132 | 509 | 463 | 258 | 145 | 115 | 84 | 60 | 55 | 54 | 28 | 18 | 10 | 13 | 12 | 18 | 43 | 39 | 35 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | on | on | on | on | off | off | off | off | off | off | off | off | off | off | off | cross-off | glassy | glassy | on | on |
High Tide | 4:34PM1.43m | 2:58AM1.36m | 4:45PM1.45m | 3:46AM1.44m | 4:57PM1.47m | 4:26AM1.51m | 5:10PM1.49m | 5:03AM1.54m | 5:25PM1.52m | 5:39AM1.55m | 5:43PM1.56m | 6:17AM1.53m | 6:04PM1.59m | ||||||||
Low Tide | 9:17AM0.35m | 9:58PM0.98m | 9:55AM0.33m | 10:20PM0.85m | 10:27AM0.35m | 10:42PM0.73m | 10:54AM0.39m | 11:05PM0.60m | 11:18AM0.46m | 11:30PM0.48m | 11:40AM0.54m | 11:59PM0.38m | 12:02PM0.63m | 00:31AM0.32m | |||||||
 | |  |  | |  |  | |  | | |  |  | |  | | | | | | | |
 | 5:18 | — | — | 5:18 | — | — | 5:20 | — | — | 5:20 | — | — | 5:20 | — | — | 5:22 | — | — | 5:22 | — | — |
 | — | 6:00 | — | — | 5:59 | — | — | 5:57 | — | — | 5:55 | — | — | 5:54 | — | — | 5:52 | — | — | 5:52 | — |
mm | — | — | — | — | — | 8 | 2 | 3 | 19 | 3 | 2 | 1 | — | — | — | — | — | — | — | — | — |
Temp °C | 28 | 28 | 27 | 29 | 29 | 22 | 20 | 20 | 19 | 19 | 20 | 20 | 21 | 22 | 22 | 25 | 27 | 26 | 26 | 27 | 26 |
Feels °C | 31 | 28 | 29 | 28 | 29 | 19 | 18 | 17 | 17 | 19 | 21 | 20 | 22 | 23 | 23 | 27 | 30 | 31 | 28 | 29 | 28 |
Swell 1 Height (m) Direction Period (s) | S 9 | E 10 | SSW 10 | E 12 | — | S 9 | S 9 | S 8 | S 8 | S 8 | S 8 | S 7 | S 7 | SSW 7 | SSW 7 | SE 9 | SE 9 | SE 8 | SE 9 | SE 9 | SE 8 |
| kJ | 276 | 2 | 132 | 3 | — | 258 | 145 | 115 | 84 | 60 | 55 | 54 | 28 | 18 | 10 | 13 | 12 | 18 | 43 | 39 | 35 |
Swell 2 Height (m) Direction Period (s) | SSE 8 | SSE 8 | ESE 10 | SE 12 | SE 10 | ESE 9 | — | ESE 9 | E 16 | E 10 | SE 11 | SE 9 | SE 10 | SE 10 | SE 9 | SSW 7 | SSW 7 | SSW 7 | SW 7 | S 7 | SW 8 |
| kJ | 184 | 140 | 10 | 6 | 24 | 8 | — | 9 | 5 | 2 | 4 | 3 | 4 | 4 | 3 | 5 | 5 | 5 | 2 | 1 | 3 |
Swell 3 Height (m) Direction Period (s) | SE 10 | ESE 10 | SE 12 | E 17 | E 16 | SE 11 | E 15 | E 15 | E 14 | E 14 | E 15 | S 8 | E 14 | E 14 | E 13 | E 13 | E 13 | — | S 10 | S 9 | S 10 |
| kJ | 16 | 10 | 6 | 6 | 5 | 5 | 4 | 17 | 16 | 4 | 4 | 1 | 4 | 4 | 4 | 3 | 3 | — | 2 | 2 | 2 |
Wind waves Height (m) Direction Period (s) | — | S 9 | S 8 | SSW 8 | S 9 | NNE 4 | N 3 | NNE 3 | NNE 3 | — | — | NNE 2 | — | — | — | — | — | — | — | — | — |
| kJ | — | 276 | 122 | 509 | 463 | 11 | 6 | 6 | 2 | — | — | 1 | — | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 85 | 19 | 748 | 128 | 222 | 0 | 30 | 0 | 0 | 0 | 2 | 45 | 57 | 24 | 57 | 24 | 30 | 24 | 64 | 30 |
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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