Surf Forecasts:
Rock Island surf forecast from 23 Aug 2026:
- Best quality surf: Monday 24 Aug, 6AM (local time) - 1.5ft (0.5m), 16s period, SSE swell with glassy winds.
- Most powerful swell: Monday 24 Aug, 9PM (local time) - 5ft (1.5m), 14s period, SSE swell with 911 kJ wave energy.
- Next surfable swell (1★+): Monday 24 Aug, 6AM (local time) - 1.5ft (0.5m), 16s period with SSE swell.
Best Forecast Surf Conditions for Rock Island this week:
The surf forecast for Rock Island over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Monday (Aug 24) at 6AM. The primary swell is predicted to be 0.5m and 16s period with a secondary swell of 0.5m and 12s. The wind is predicted to be glassy as the swell arrives.
The most powerful waves expected at Rock Island in the next 16 days are 1.5m 14s and forecast to arrive on Monday (Aug 24) at 9PM. Winds are predicted to be 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+) | 6AM (Mon 24th Aug) | 1.5ft (0.5m) 16s |
| Best Surf | 6AM (Mon 24th Aug) | 1.5ft (0.5m) 16s |
| Most Powerful | 9PM (Mon 24th Aug) | 5ft (1.5m) 14s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright, let’s break it down in feet and Fahrenheit. Rusty here, checkin’ in on Rock Island.
Water temp is right around 81°F — nothing unusual there for this time of year.
The next couple weeks start off slow. From Sunday the 23rd through most of August and into early September, it’s a whole lot of flat, messy, or blown-out junk. Wave energy readings are low, often under 100, and the swell is tiny — under 1ft to barely 2ft. Winds are mostly onshore or strong. Not worth the wax.
There’s a big gap of about a week with no real reason to get wet.
Wednesday, September 2nd finally turns things around. Morning at Rock Island shows a 1ft swell from the SSW, period at 13 seconds — that’s a nice long groundswell. Combined energy jumps to 521 (moderate). Wind is offshore from the NE at 15 mph, clean and glassy. For a reef break that’s fairly consistent and open to south swell, this is prime. Beginners can handle this size, but you might run into a few others since crowds are possible here sometimes.
Thursday, September 3rd keeps the momentum. Morning and afternoon both bring 4ft to 5ft SSW swell, period 13–14 seconds — very long period groundswell. Energy is strong at 617 and 557. Offshore winds from the NNE at 20–25 mph keep it clean. This is the best stretch of the whole forecast.
After that, it fades fast. Friday the 4th has size but strong winds and only marginal conditions. By the weekend into the next week, it’s stormy, blown-out, and small again. Near gale force cross-onshore winds by the 7th — not a paddle session.
So the call is clear: Wednesday and Thursday, September 2nd and 3rd. That’s your window. Clean, solid, lined-up groundswell with offshore wind. Don’t sleep on it.
Rusty.
Short Range ForecastLight rain (total 2mm), mostly falling on Tue night. Warm (max 29°C on Tue morning, min 25°C on Sun night). Winds increasing (calm on Sun night, fresh winds from the S by Tue afternoon). | Days 5-7 Weather SummaryHeavy rain (total 35mm), heaviest during Thu night. Warm (max 29°C on Wed afternoon, min 22°C on Thu night). Wind will be generally light. | |||||||||||||||||||
Sun 23 | Monday 24 | Tuesday 25 | Wednesday 26 | Thursday 27 | Friday 28 | Saturday 29 | ||||||||||||||
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) | SE 13 | SE 13 | SSE 18 | SSE 16 | SSE 14 | SSE 13 | S 12 | S 13 | S 12 | SSW 12 | SSW 12 | SSW 11 | SW 10 | S 9 | S 9 | S 8 | SSW 8 | S 8 | SSW 8 | SSW 8 |
Wave Graph  | ||||||||||||||||||||
 kJ | 27 | 82 | 260 | 480 | 615 | 690 | 347 | 448 | 341 | 267 | 156 | 46 | 27 | 57 | 52 | 35 | 22 | 35 | 22 | 23 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | on | on | on | on | on | on | cross-on | on | on | cross-off | off | off | glassy | on | on | cross-off | off | cross-on | cross-off |
High Tide | 3:38PM1.26m | 11:45PM1.35m | 4:17PM1.34m | 1:21AM1.36m | 4:45PM1.39m | 2:39AM1.41m | 5:10PM1.43m | 3:40AM1.47m | 5:33PM1.46m | 4:32AM1.53m | 5:56PM1.47m | 5:19AM1.57m | 6:18PM1.49m | |||||||
Low Tide | 6:54PM1.21m | 8:12AM0.33m | 8:44PM1.17m | 9:11AM0.27m | 9:41PM1.08m | 10:00AM0.23m | 10:21PM0.97m | 10:42AM0.22m | 10:57PM0.85m | 11:20AM0.24m | 11:30PM0.73m | 11:54AM0.30m | 00:05AM0.62m | |||||||
 |  |  | |  | | |  |  | | | |  |  | | | | |  |  | |
 | — | — | 5:07 | — | — | 5:07 | — | — | 5:07 | — | — | 5:09 | — | — | 5:09 | — | — | 5:11 | — | — |
 | 6:22 | — | — | 6:20 | — | — | 6:19 | — | — | 6:17 | — | — | 6:15 | — | — | 6:15 | — | — | 6:14 | — |
mm | — | — | — | — | — | — | — | 1 | 1 | — | 2 | 3 | 7 | 22 | — | — | 1 | — | 1 | 1 |
Temp °C | 28 | 26 | 27 | 28 | 27 | 29 | 28 | 27 | 28 | 29 | 28 | 26 | 26 | 23 | 26 | 27 | 27 | 28 | 28 | 26 |
Feels °C | 30 | 30 | 29 | 29 | 28 | 30 | 27 | 26 | 30 | 30 | 31 | 30 | 26 | 26 | 27 | 28 | 30 | 29 | 30 | 29 |
Swell 1 Height (m) Direction Period (s) | SSW 8 | SE 13 | SSE 18 | SSE 13 | SSE 14 | SSE 13 | S 12 | S 13 | S 12 | SSW 12 | SSW 12 | SSW 11 | S 6 | S 9 | S 9 | S 8 | SSW 5 | S 8 | SSW 8 | SSW 8 |
| kJ | 14 | 82 | 260 | 342 | 615 | 690 | 347 | 448 | 341 | 267 | 156 | 46 | 26 | 57 | 52 | 35 | 9 | 35 | 22 | 23 |
Swell 2 Height (m) Direction Period (s) | SE 13 | SSW 8 | SSE 12 | SSE 16 | S 17 | E 14 | S 14 | E 13 | SE 10 | SSE 9 | SSE 9 | S 5 | SW 10 | SSE 10 | SSE 9 | SSE 10 | SSW 8 | SSE 11 | SSE 11 | SSE 10 |
| kJ | 27 | 14 | 133 | 480 | 270 | 4 | 268 | 3 | 24 | 48 | 32 | 14 | 27 | 9 | 8 | 9 | 22 | 11 | 12 | 11 |
Swell 3 Height (m) Direction Period (s) | SE 10 | SSE 18 | SSE 15 | SW 8 | ESE 15 | — | E 13 | ESE 13 | E 12 | E 12 | E 11 | SSE 9 | S 9 | SW 9 | SW 9 | SW 9 | SSE 9 | S 13 | NNE 2 | SE 10 |
| kJ | 4 | 31 | 84 | 3 | 42 | — | 3 | 33 | 3 | 3 | 2 | 33 | 15 | 14 | 3 | 3 | 9 | 3 | 1 | 4 |
Wind waves Height (m) Direction Period (s) | S 4 | — | — | S 3 | SSW 4 | SSW 4 | SSW 4 | SSW 5 | SW 4 | SSW 4 | SSW 5 | — | NNE 3 | — | — | — | — | NNE 2 | — | — |
| kJ | 1 | — | — | 4 | 14 | 10 | 43 | 20 | 9 | 25 | 33 | — | 1 | — | — | — | — | 1 | — | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 51 | 14 | 18 | 77 | 14 | 14 | 249 | 27 | 14 | 518 | 0 | 0 | 0 | 0 | 92 | 38 | 16 | 38 | 16 | 38 |
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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