Surf Forecasts:
Rock Island surf forecast from 12 Aug 2026:
- Best quality surf: Thursday 13 Aug, 3PM (local time) - 1.5ft (0.5m), 10s period, S swell with glassy winds.
- Most powerful swell: Saturday 15 Aug, 6PM (local time) - 3ft (0.9m), 10s period, SE swell with 151 kJ wave energy.
- Next surfable swell (1★+): Thursday 13 Aug, 3PM (local time) - 1.5ft (0.5m), 10s period with S 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 13) at 3PM. The primary swell is predicted to be 0.5m and 10s period with a secondary swell of 0.1m and 10s. 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 0.9m 10s and forecast to arrive on Saturday (Aug 15) at 6PM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Thursday (Aug 13) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3PM (Thu 13th Aug) | 1.5ft (0.5m) 10s |
| Best Surf | 3PM (Thu 13th Aug) | 1.5ft (0.5m) 10s |
| Most Powerful | 6PM (Sat 15th Aug) | 3ft (0.9m) 10s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright mate, Rusty here. Let's have a look at what Rock Island (Rock Island) has got cooking for the next couple of weeks.
First up, the water temp is sitting about average for this time of year, nothing too wild. The pattern for the next week or so is pretty grim, to be honest. We've got a real flat spell on the cards. There's a bit of knee-high, weak swell from the south, but the conditions are just ordinary. Morning offshore winds on Thursday the 13th and Friday the 14th keep things clean, but the wave energy is weak (55). The surf is there but it's nothing to get excited about. Saturday the 15th sees a little bump in energy to moderate (212) with a 3ft SE swell, but it's cross-shore wind, making for a messy, marginal surf. The whole stretch from Thursday the 13th right through to Monday the 24th is a real struggle. There are plenty of "poor surf conditions" days, with the odd morning that's "surfable but very ordinary." A few glassy mornings pop up, like Tuesday the 18th and Saturday the 22nd, but the swell is tiny—0.7ft to 2ft—so you're just bobbing around. It's a long, boring run.
Now, here's the flash. Mark your calendars for Tuesday the 25th of August. That morning, things absolutely switch on. We're looking at a solid 8ft south-southeast swell with a very long period of 17 seconds, pumping in a massive 3646 energy reading. The wind is a light, cross-offshore breeze from the east, making it clean. This is serious groundswell, and for a reef break like Rock Island, that long period is going to produce some proper, well-shaped lines. It's going to be big, powerful, and definitely for experienced surfers only. The afternoon on the 25th looks average with onshore wind, so get it in the morning.
Wednesday the 26th of August morning is still a solid option, with a 4ft south-southeast swell and an 11-second period, moderate energy (684), and clean cross-offshore winds again. It's a good follow-up session, but the 25th is the real standout.
That's the story. A long, flat patch to sit through, but a ripper day on the 25th morning makes it all worth waiting for. Stay patient.
Rusty.
Short Range ForecastHeavy rain (total 37mm), heaviest during Thu night. Warm (max 29°C on Thu afternoon, min 24°C on Sat night). Wind will be generally light. | Days 4-6 Weather SummaryMostly dry. Warm (max 28°C on Tue afternoon, min 23°C on Sun night). Wind will be generally light. | ||||||||||||||||||||
Thursday 13 | Friday 14 | Saturday 15 | Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | |||||||||||||||
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) | SSW 10 | S 10 | SSW 9 | SSW 9 | SSW 9 | ESE 10 | SSW 11 | ESE 9 | SSW 9 | SSW 10 | SSW 10 | SE 10 | SSW 9 | SSW 9 | SSW 8 | SSW 8 | S 7 | SSE 6 | SSE 8 | SSE 9 | S 9 |
Wave Graph  | |||||||||||||||||||||
 kJ | 38 | 47 | 28 | 16 | 29 | 88 | 40 | 121 | 28 | 33 | 31 | 28 | 26 | 15 | 14 | 14 | 8 | 8 | 40 | 80 | 78 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | off | glassy | off | off | cross-off | cross-off | cross-off | cross | off | off | cross-off | cross-off | cross-off | cross-on | on | cross-on | on | glassy | cross-off | cross-on | cross-on |
High Tide | 6:08PM1.47m | 4:55AM1.54m | 6:31PM1.48m | 5:41AM1.56m | 6:55PM1.48m | 6:26AM1.55m | 7:18PM1.48m | 7:12AM1.50m | 7:41PM1.48m | 8:00AM1.43m | 8:06PM1.47m | 8:53AM1.34m | 8:32PM1.46m | ||||||||
Low Tide | 11:12AM0.14m | 11:25PM0.88m | 11:48AM0.17m | 00:00AM0.78m | 12:23PM0.24m | 00:35AM0.68m | 12:57PM0.34m | 1:12AM0.59m | 1:28PM0.46m | 1:51AM0.52m | 1:59PM0.61m | 2:34AM0.48m | 2:29PM0.75m | ||||||||
 |  |  | | | | | |  |  | |  |  | | | | | | | | | |
 | 4:58 | — | — | 4:58 | — | — | 5:00 | — | — | 5:01 | — | — | 5:01 | — | — | 5:01 | — | — | 5:03 | — | — |
 | — | 6:34 | — | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — | — | 6:29 | — | — | 6:28 | — | — | 6:27 | — |
mm | 1 | 4 | 9 | 2 | 3 | 16 | 1 | 1 | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 27 | 29 | 27 | 27 | 28 | 27 | 27 | 29 | 25 | 27 | 27 | 25 | 26 | 27 | 26 | 27 | 28 | 26 | 28 | 28 | 26 |
Feels °C | 28 | 33 | 30 | 28 | 30 | 30 | 27 | 30 | 25 | 27 | 27 | 25 | 28 | 28 | 28 | 29 | 30 | 29 | 31 | 31 | 30 |
Swell 1 Height (m) Direction Period (s) | SSW 10 | S 10 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 11 | SE 8 | SSW 9 | SSW 10 | SSW 10 | SSW 9 | SSW 9 | SSW 9 | SSW 8 | SSW 8 | SSW 8 | SSE 6 | SSE 8 | SSE 9 | S 9 |
| kJ | 38 | 47 | 28 | 16 | 29 | 16 | 40 | 32 | 28 | 33 | 31 | 27 | 26 | 15 | 14 | 14 | 7 | 8 | 40 | 80 | 78 |
Swell 2 Height (m) Direction Period (s) | SSE 4 | E 10 | ESE 9 | S 12 | ESE 6 | SSE 10 | SE 5 | SSW 10 | SE 8 | ESE 10 | SE 10 | SE 10 | ESE 10 | ESE 10 | SE 10 | SE 10 | SE 10 | SE 10 | SW 8 | — | SE 10 |
| kJ | 2 | 2 | 8 | 11 | 6 | 20 | 10 | 34 | 21 | 9 | 15 | 28 | 10 | 10 | 4 | 4 | 4 | 4 | 3 | — | 4 |
Swell 3 Height (m) Direction Period (s) | SE 11 | SE 12 | S 12 | SE 7 | SE 11 | SE 6 | SSE 9 | ESE 10 | ESE 10 | SSE 7 | SSE 11 | SSE 11 | SSE 11 | SSE 11 | SE 7 | S 7 | E 8 | SSW 8 | SE 10 | SW 9 | — |
| kJ | 5 | 5 | 11 | 2 | 5 | 5 | 16 | 10 | 9 | 5 | 12 | 12 | 12 | 11 | 2 | 1 | 6 | 7 | 4 | 3 | — |
Wind waves Height (m) Direction Period (s) | NE 3 | — | — | — | — | ESE 10 | — | ESE 9 | ENE 2 | NE 2 | — | — | — | — | SSE 2 | — | S 7 | — | — | — | S 3 |
| kJ | 2 | — | — | — | — | 88 | — | 121 | 1 | 1 | — | — | — | — | 1 | — | 8 | — | — | — | 1 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 38 | 0 | 38 | 38 | 38 | 0 | 17 | 491 | 0 | 38 | 38 | 0 | 38 | 16 | 64 | 51 | 18 | 51 | 16 | 38 | 6 |
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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