Surf Forecasts:
Rock Island surf forecast from 26 Aug 2026:
- Best quality surf: Tuesday 1 Sep, 9AM (local time) - 2.5ft (0.8m), 13s period, S swell with offshore winds.
- Most powerful swell: Wednesday 2 Sep, 3AM (local time) - 4ft (1.2m), 12s period, SSW swell with 461 kJ wave energy.
- Next surfable swell (1★+): Thursday 27 Aug, 12PM (local time) - 2.5ft (0.8m), 6s period with SSW 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 Thursday (Aug 27) at 12PM. The primary swell is predicted to be 0.8m and 6s period with a secondary swell of 0.6m and 6s. Another secondary swell of 0.4m and 11s is also forecast. 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 1.2m 12s and forecast to arrive on Wednesday (Sep 02) at 3AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Monday (Aug 31) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12PM (Thu 27th Aug) | 2.5ft (0.8m) 6s |
| Best Surf | 9AM (Tue 1st Sep) | 2.5ft (0.8m) 13s |
| Most Powerful | 3AM (Wed 2nd Sep) | 4ft (1.2m) 12s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Hey, Rusty here again. Let's break down Rock Island in feet and fahrenheit.
Like I said, there's a real dry spell to start. First decent surf isn't until the 1st of September, so a full week of watching the horizon.
The Outlook
Rock Island (reef)
The water is warm, about 82°, which is normal for the season.
The first real window opens on Tuesday morning, 1st September. We’ve got a clean 3ft south swell, with a 13-second period. That's proper groundswell, and with a moderate offshore breeze from the north-northeast, it’ll be clean. The wave energy is moderate (211). This is a solid, clean start. The afternoon brings it up to 3ft from the south, 12-second period, energy at 301. It’s a little cross-offshore, but still good. This is a standout. Crowds are possible, so get in the water early.
Wednesday, 2nd September is a washout. Swell is 4ft, strong energy (365), but the south-southeast wind is onshore with rain, making it choppy. Skip it.
A bigger swell hits Thursday and Friday, 4th and 5th September, but the wind is howling onshore from the south-southwest. Thursday morning has 5ft, strong energy (603), but it's blown out. Friday is 4ft from the south, energy at 315. This is more for the kite surfers.
The wind stays onshore for days, so we wait.
The next highlight is Tuesday, 8th September. Swell comes back to 4ft from the south, 12-second period, strong energy (350). The wind is a light cross-offshore from the east-northeast, keeping it clean. Good session.
Wednesday, 9th September is the absolute pick of the second week. The morning is glassy, with a 4ft south swell, 12-second period, and strong energy (393). The afternoon is glassy too, 4ft from the south, 11-second period, energy at 398. This is a proper standout. Clean, consistent, and plenty of power.
After that, Thursday, 10th September the onshore wind comes back and the quality drops. The swell is still there, but it's a mess.
Best bets: the morning of the 1st, the morning of the 8th, and the whole of the 9th. The 9th is the one to pencil in.
Rusty.
Short Range ForecastModerate rain (total 13mm), heaviest on Thu night. Warm (max 31°C on Wed afternoon, min 24°C on Thu night). Mainly fresh winds. | Days 5-7 Weather SummaryLight rain (total 4mm), mostly falling on Sat afternoon. Warm (max 28°C on Sun afternoon, min 24°C on Sat afternoon). Wind will be generally light. | |||||||||||||||||||
Wed 26 | Thursday 27 | Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | Tuesday 1 | ||||||||||||||
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) | SSW 12 | SSW 11 | SSW 6 | S 11 | S 10 | SSW 6 | SW 6 | SSW 5 | SSW 8 | SSW 8 | SSW 8 | SSW 8 | SSW 5 | SSW 6 | SSW 14 | SSW 12 | S 10 | S 13 | S 12 | S 12 |
Wave Graph  | ||||||||||||||||||||
 kJ | 137 | 68 | 36 | 55 | 45 | 61 | 54 | 16 | 20 | 12 | 12 | 11 | 31 | 103 | 36 | 30 | 98 | 202 | 295 | 453 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | on | on | off | on | glassy | glassy | cross-off | cross-off | glassy | off | glassy | on | cross-on | cross-off | off | off | off | cross-off | cross |
High Tide | 5:10PM1.43m | 3:40AM1.47m | 5:33PM1.46m | 4:32AM1.53m | 5:56PM1.47m | 5:19AM1.57m | 6:18PM1.49m | 6:04AM1.58m | 6:41PM1.49m | 6:48AM1.55m | 7:03PM1.50m | 7:33AM1.49m | 7:26PM1.50m | |||||||
Low Tide | 10:21PM0.97m | 10:42AM0.22m | 10:57PM0.85m | 11:20AM0.24m | 11:30PM0.73m | 11:54AM0.30m | 00:05AM0.62m | 12:27PM0.39m | 00:39AM0.52m | 12:58PM0.50m | 1:16AM0.45m | 1:29PM0.63m | 1:56AM0.40m | |||||||
 |  |  | |  |  |  |  | |  |  | | | | | | | | |  | |
 | — | — | 5:09 | — | — | 5:09 | — | — | 5:11 | — | — | 5:11 | — | — | 5:11 | — | — | 5:13 | — | — |
 | 6:17 | — | — | 6:15 | — | — | 6:15 | — | — | 6:14 | — | — | 6:12 | — | — | 6:10 | — | — | 6:09 | — |
mm | — | — | 2 | 2 | 9 | — | — | — | — | 1 | 2 | — | — | — | 1 | — | — | — | — | 5 |
Temp °C | 31 | 28 | 28 | 26 | 25 | 26 | 27 | 27 | 26 | 25 | 24 | 25 | 28 | 28 | 24 | 25 | 25 | 27 | 28 | 27 |
Feels °C | 33 | 29 | 32 | 24 | 25 | 30 | 32 | 31 | 28 | 28 | 26 | 27 | 31 | 32 | 24 | 27 | 27 | 28 | 29 | 30 |
Swell 1 Height (m) Direction Period (s) | SSW 12 | SSW 11 | S 6 | S 11 | S 10 | S 6 | SSW 8 | SSW 5 | SSW 8 | SSW 8 | SSW 8 | SSW 8 | SSE 10 | SSW 6 | S 6 | SSW 6 | S 10 | S 13 | S 12 | S 12 |
| kJ | 137 | 68 | 24 | 55 | 45 | 19 | 53 | 16 | 20 | 12 | 12 | 11 | 10 | 43 | 20 | 10 | 98 | 202 | 295 | 453 |
Swell 2 Height (m) Direction Period (s) | SSE 9 | SSE 9 | SSE 9 | SE 10 | SSW 6 | S 9 | SSE 10 | S 8 | SSE 11 | SSE 11 | SSE 10 | SSE 10 | S 8 | SSE 10 | SSW 14 | SSW 12 | SSE 10 | SSE 10 | SE 10 | SE 10 |
| kJ | 49 | 31 | 28 | 24 | 10 | 14 | 9 | 12 | 11 | 12 | 10 | 10 | 1 | 10 | 36 | 30 | 9 | 9 | 4 | 4 |
Swell 3 Height (m) Direction Period (s) | E 12 | S 10 | SW 10 | SW 10 | SSE 10 | SSE 9 | SW 9 | SSE 10 | — | E 11 | SE 10 | E 11 | — | S 13 | SSE 10 | S 11 | E 12 | — | E 11 | E 10 |
| kJ | 3 | 19 | 25 | 15 | 9 | 8 | 3 | 9 | — | 10 | 4 | 2 | — | 13 | 10 | 20 | 3 | — | 2 | 2 |
Wind waves Height (m) Direction Period (s) | SSW 4 | SSW 5 | SSW 6 | SSW 6 | — | SSW 6 | SW 6 | — | — | — | — | — | SSW 5 | SSW 6 | NE 3 | NE 2 | NE 3 | NNE 3 | — | — |
| kJ | 28 | 39 | 36 | 28 | — | 61 | 54 | — | — | — | — | — | 31 | 103 | 2 | 1 | 1 | 1 | — | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 27 | 27 | 14 | 38 | 38 | 0 | 0 | 38 | 51 | 64 | 51 | 16 | 522 | 12 | 38 | 0 | 0 | 0 | 0 | 12 |
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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