Surf Forecasts:
Rock Island surf forecast from 11 Sep 2026:
- Most powerful swell: Friday 18 Sep, 3PM (local time) - 5.5ft (1.7m), 17s period, SSE swell with 1,497 kJ wave energy.
Best Forecast Surf Conditions for Rock Island this week:
The most powerful waves expected at Rock Island in the next 16 days are 1.7m 17s and forecast to arrive on Friday (Sep 18) 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 0.6m 3s period and expected on Friday (Sep 18) at 3AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 3PM (Fri 18th Sep) | 5.5ft (1.7m) 17s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright, this is Rusty.
Gotta be honest with you, Rock Island is flat as a pancake right now. Nothing doing for the first week. The swell energy is tiny (33), and it’s just rain and onshore breezes. We’re looking at a solid seven-day gap with nothing but poor surf conditions until the 18th of September.
Then, things finally change. On Friday the 18th of September, the ocean delivers. A pulse of energy hits with combined swell energy of 645. The swell is 4ft from the SSE with a very long period of 16 seconds. That’s proper groundswell, and with a fresh NNE offshore wind, it’ll be clean. That long a period (over 15 seconds) can make a beach break stand up straight, but there’s plenty of power.
The big standout is Saturday the 19th of September. This is the one. We’ve got 7ft of solid SSE swell with a 14-second period and energy reading 1469. The wind is a moderate NNE offshore, keeping the faces clean. This is excellent surf, but at over 7ft, it’s for experts only. Sunday the 20th still has 5ft with glassy conditions in the afternoon—a great option for the rest of us.
The water is 82°, which is a touch warmer than average.
After that, Wednesday the 23rd offers 6ft with clean offshore wind, but it’s dropping. Then another big window arrives on the 25th and 26th. Saturday the 26th is the second standout: 7ft of long-period SSE swell (16 seconds) and a gentle offshore breeze. The combined energy is a massive 2325. Again, that’s expert territory, and the super-long period means it’ll be walling up.
On the big days, this beach break setup looks more interesting for kite surfing than paddle surfing. If you’re an experienced surfer, the 19th and the 26th are your days.
Rusty.
Short Range ForecastHeavy rain (total 44mm), heaviest during Fri morning. Warm (max 24°C on Sun afternoon, min 19°C on Fri morning). Wind will be generally light. | Days 4-6 Weather SummaryModerate rain (total 13mm), heaviest on Wed night. Warm (max 27°C on Tue morning, min 22°C on Wed night). Winds decreasing (fresh winds from the S on Mon afternoon, calm by Wed afternoon). | ||||||||||||||||||||
Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | Tuesday 15 | Wednesday 16 | Thursday 17 | |||||||||||||||
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 8 | S 8 | SSW 8 | SSW 7 | SSW 7 | SSW 7 | SE 9 | SE 8 | SE 7 | SE 9 | SE 10 | SE 9 | SSE 8 | SE 8 | SE 7 | SSE 7 | SSE 8 | SE 8 | SE 8 | SSE 9 | SSE 21 |
Wave Graph  | |||||||||||||||||||||
 kJ | 28 | 28 | 19 | 18 | 18 | 9 | 13 | 18 | 14 | 19 | 14 | 29 | 40 | 31 | 23 | 19 | 26 | 17 | 9 | 8 | 42 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | off | off | off | off | off | off | off | cross-on | on | on | on | on | on | on | on | on | glassy | cross-off | off | off | cross-off |
High Tide | 5:19PM1.47m | 4:56AM1.56m | 5:41PM1.48m | 5:41AM1.58m | 6:03PM1.50m | 6:24AM1.58m | 6:25PM1.51m | 7:08AM1.53m | 6:48PM1.52m | 7:55AM1.46m | 7:12PM1.51m | 8:47AM1.38m | 7:38PM1.50m | ||||||||
Low Tide | 10:49AM0.32m | 11:01PM0.69m | 11:24AM0.37m | 11:34PM0.56m | 11:58AM0.45m | 00:08AM0.45m | 12:29PM0.55m | 00:43AM0.37m | 12:59PM0.67m | 1:21AM0.32m | 1:28PM0.80m | 2:02AM0.31m | 1:57PM0.92m | 2:48AM0.33m | |||||||
 |  |  |  | |  |  |  |  | | |  | |  |  | | |  | | |  | |
 | 5:20 | — | — | 5:20 | — | — | 5:22 | — | — | 5:22 | — | — | 5:22 | — | — | 5:24 | — | — | 5:24 | — | — |
 | — | 5:55 | — | — | 5:53 | — | — | 5:52 | — | — | 5:51 | — | — | 5:50 | — | — | 5:47 | — | — | 5:46 | — |
mm | 19 | 2 | 15 | 6 | 1 | 1 | — | — | — | — | — | — | — | — | 3 | — | 1 | 9 | 3 | 1 | — |
Temp °C | 19 | 20 | 20 | 20 | 21 | 21 | 23 | 24 | 24 | 26 | 26 | 26 | 27 | 27 | 25 | 24 | 24 | 23 | 21 | 21 | 21 |
Feels °C | 20 | 20 | 20 | 19 | 21 | 22 | 25 | 27 | 27 | 27 | 25 | 27 | 28 | 27 | 27 | 28 | 29 | 24 | 20 | 19 | 18 |
Swell 1 Height (m) Direction Period (s) | S 8 | S 8 | SSW 8 | SSW 7 | SSW 7 | SSW 7 | SE 9 | SE 8 | SE 7 | SE 9 | SE 10 | SE 9 | SSE 8 | SE 8 | SE 7 | SSE 7 | SSE 8 | SE 8 | SSE 9 | SSE 9 | SE 8 |
| kJ | 28 | 28 | 19 | 18 | 18 | 9 | 13 | 18 | 14 | 19 | 14 | 29 | 40 | 31 | 23 | 19 | 26 | 17 | 8 | 8 | 11 |
Swell 2 Height (m) Direction Period (s) | SE 10 | SE 10 | SE 10 | SE 10 | SE 10 | SE 9 | SSW 7 | SSW 7 | SW 7 | S 7 | E 12 | S 7 | S 7 | — | E 13 | SE 9 | E 13 | E 12 | SE 8 | ESE 7 | SSE 21 |
| kJ | 4 | 4 | 4 | 4 | 4 | 3 | 5 | 5 | 2 | 1 | 11 | 1 | 1 | — | 13 | 3 | 13 | 3 | 9 | 5 | 42 |
Swell 3 Height (m) Direction Period (s) | S 9 | S 8 | S 8 | S 8 | E 14 | E 13 | E 13 | E 13 | — | E 12 | E 15 | S 7 | S 7 | — | S 7 | — | S 8 | — | E 12 | E 11 | SSE 8 |
| kJ | 1 | 1 | 1 | 1 | 4 | 4 | 3 | 3 | — | 3 | 4 | 1 | 1 | — | 1 | — | 1 | — | 3 | 2 | 7 |
Wind waves Height (m) Direction Period (s) | — | — | NNE 2 | NNE 3 | NNE 2 | NNE 2 | — | — | — | — | S 4 | S 4 | — | S 2 | — | — | — | NE 2 | NNE 3 | N 3 | NNE 3 |
| kJ | — | — | 1 | 1 | 1 | 1 | — | — | — | — | 12 | 7 | — | 1 | — | — | — | 1 | 1 | 5 | 6 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 51 | 54 | 51 | 55 | 51 | 38 | 16 | 16 | 51 | 18 | 77 | 38 | 38 | 77 | 38 | 18 | 16 | 51 | 55 | 145 | 61 |
Best forecast wave conditions in Kanagawa | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
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Information about the Rock Island Surf forecast
The above surf forecast table for Rock Island provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Rock Island can be found by selecting the local surf guide option on the grey menu. Our Rock Island 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 (Rock Island) 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 Rock Island 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.
Rock Island is 3 km (2 miles) from the city of Kamakura. If you plan a holiday in Kanagawa, look for hotels and other accommodation in Kamakura. Kamakura has rooms for a wide range of budgets as well as car hire and transport links.
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