Surf Forecasts:
Rock Island surf forecast from 16 Aug 2026:
- Most powerful swell: Monday 24 Aug, 9AM (local time) - 5ft (1.5m), 16s period, SSE swell with 1,164 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 1.5m 16s and forecast to arrive on Monday (Aug 24) at 9AM. Winds are predicted to be onshore at the time the swell arrives.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 9AM (Mon 24th Aug) | 5ft (1.5m) 16s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Right folks, Rusty here. Let’s have a look at what’s on the cards for Rock Island over the next couple of weeks.
To be straight up with you, the first week is pretty bleak. We’ve got a long stretch from Monday the 17th of August right through to Sunday the 23rd where there’s nothing worth paddling out for. The swell is tiny, mostly under 2ft, and on top of that, the wind is nuking onshore from the SSW most days, especially from the 21st onwards. It’s just not gonna happen. That’s a solid week of sitting on the beach.
Things finally start to change on Monday the 24th of August. A big groundswell fills in from the SSE, pushing waves up to 5ft in the morning and 6ft in the afternoon. That’s an absolutely massive ramp-up in energy – we’re talking combined swell energy readings of 1216 and 1598! But here’s the kicker: the wind is still howling onshore from the SSW at 15-18 mph. That is going to turn it into a blown-out mess. The period is 16 seconds, which means it’s a proper long-period groundswell, perfect for a reef set-up like Rock Island, but the onshore wind will ruin it. This is really only for experts if they’re desperate.
That sloppy, windy theme continues through the 25th, 26th, 27th, and 28th. We get some solid size – swells up to 8ft on the 28th – but with the constant onshore wind, the quality is poor. It’s going to look more like a kitesurfing zone than a surf break. The energy is still very high, with readings over 1000 on several days, but it's just not clean.
Finally, there’s a light at the end of the tunnel. On Saturday the 29th of August, the wind shifts to a cross-offshore from the East at 6 mph. The swell drops back to 3ft from the SSW with a solid 12-second period. The combined energy is 307, so it’s moderate, but more importantly, it’s *clean*. That morning session is the best bet so far. It’s not huge, but it’s surfable.
Then, we have a potential standout on Monday the 31st of August. The models are showing a massive 16ft SSE swell with an 18-second period hitting early in the morning. The wind is light cross-off from the NE at 6 mph. The combined energy reading is a colossal 15811! This is a huge, powerful groundswell. The catch is that the guidance says it’s predicted to be too big for this break, so you’d need to be an absolute expert and know the reef well. It will be intense. The afternoon drops to 13ft with the wind still clean. If you are a big-wave charger, that Monday morning is the call, but it’s a week and a half away, so take it with a pinch of salt.
Looking into September, Tuesday the 1st sees some glassy offshore NE wind at 15 mph with an 12ft SSE swell. That’s a lot of wind but it’s offshore, so it might be groomed, though still very big and only for experts.
Honestly, for the average surfer, the clean window on the morning of Saturday the 29th of August is the most realistic target. The water temp is 81°, which is about average for this time of year.
Stay patient, and keep an eye on those longer-range charts.
Rusty.
Short Range ForecastLight rain (total 2mm), mostly falling on Mon night. Warm (max 28°C on Mon afternoon, min 24°C on Tue night). Wind will be generally light. | Days 4-6 Weather SummaryMostly dry. Warm (max 27°C on Thu morning, min 26°C on Thu morning). Winds increasing (light winds from the ESE on Thu morning, fresh winds from the S by Sat afternoon). | ||||||||||||||||||||
Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | |||||||||||||||
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 | SSW 8 | SSW 8 | SSW 8 | SSW 8 | SE 7 | SE 6 | SE 6 | SE 6 | SSE 6 | SSW 9 | SSW 8 | SSW 8 | S 8 | SSW 10 | SSW 10 | SSW 10 | SSW 10 | SSW 9 | SSW 9 | SSE 17 |
Wave Graph | |||||||||||||||||||||
23 | 14 | 7 | 6 | 12 | 11 | 6 | 6 | 5 | 4 | 8 | 14 | 24 | 47 | 80 | 77 | 56 | 54 | 34 | 33 | 197 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | on | cross-on | glassy | on | cross | cross-off | cross-on | cross-on | glassy | on | on | cross-on | on | on | on | on | on | on | on | on |
High Tide | 7:41PM1.48m | 8:00AM1.43m | 8:06PM1.47m | 8:53AM1.34m | 8:32PM1.46m | 9:59AM1.24m | 9:00PM1.45m | 11:32AM1.17m | 9:36PM1.42m | 1:55PM1.18m | 10:25PM1.38m | 3:38PM1.26m | 11:45PM1.35m | ||||||||
Low Tide | 1:28PM0.46m | 1:51AM0.52m | 1:59PM0.61m | 2:34AM0.48m | 2:29PM0.75m | 3:23AM0.45m | 3:00PM0.90m | 4:23AM0.44m | 3:34PM1.04m | 5:36AM0.43m | 4:30PM1.15m | 6:58AM0.39m | 6:54PM1.21m | ||||||||
5:01 | — | — | 5:01 | — | — | 5:03 | — | — | 5:03 | — | — | 5:05 | — | — | 5:05 | — | — | 5:05 | — | — | |
— | 6:29 | — | — | 6:28 | — | — | 6:27 | — | — | 6:24 | — | — | 6:23 | — | — | 6:22 | — | — | 6:22 | — | |
mm | — | — | 2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 27 | 28 | 26 | 27 | 27 | 26 | 27 | 27 | 26 | 27 | 27 | 26 | 27 | 27 | 26 | 27 | 27 | 27 | 28 | 28 | 27 |
Feels °C | 30 | 30 | 28 | 30 | 29 | 29 | 30 | 29 | 29 | 30 | 28 | 29 | 29 | 27 | 27 | 26 | 26 | 27 | 26 | 26 | 26 |
Swell 1 Height (m) Direction Period (s) | S 9 | SSW 8 | SSW 8 | SSE 5 | SSW 8 | SE 7 | SE 6 | SE 6 | SE 6 | SSE 6 | SSW 9 | SSW 8 | SSW 8 | SSW 11 | SSW 10 | SSW 10 | SSW 10 | SSW 10 | SSW 9 | SSW 9 | SSE 17 |
23 | 14 | 7 | 3 | 6 | 11 | 6 | 6 | 5 | 3 | 8 | 14 | 24 | 25 | 80 | 77 | 56 | 54 | 34 | 33 | 197 | |
Swell 2 Height (m) Direction Period (s) | SE 11 | SSE 5 | SSE 6 | SSW 8 | SE 10 | SSW 8 | SE 10 | SE 10 | SE 10 | SE 10 | SSE 6 | SE 11 | ESE 11 | SE 10 | SE 10 | SE 10 | SE 10 | SE 10 | S 4 | SSE 17 | SE 12 |
5 | 3 | 3 | 6 | 4 | 6 | 4 | 4 | 4 | 4 | 3 | 4 | 11 | 4 | 4 | 4 | 4 | 4 | 6 | 30 | 55 | |
Swell 3 Height (m) Direction Period (s) | E 9 | SE 11 | SE 10 | SE 10 | SSW 8 | SE 10 | SW 8 | SW 8 | S 8 | SW 8 | SE 11 | SSE 5 | S 12 | E 6 | S 9 | SE 11 | SE 11 | SE 11 | SE 10 | SSE 13 | SW 9 |
1 | 4 | 4 | 4 | 12 | 4 | 2 | 3 | 1 | 2 | 4 | 3 | 3 | 1 | 2 | 4 | 5 | 5 | 4 | 17 | 21 | |
Wind waves Height (m) Direction Period (s) | — | — | — | — | SSE 6 | — | — | — | — | — | — | — | — | S 8 | S 3 | SSW 3 | S 4 | SSW 4 | — | S 4 | S 4 |
— | — | — | — | 7 | — | — | — | — | — | — | — | — | 47 | 8 | 4 | 14 | 12 | — | 9 | 7 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 51 | 18 | 51 | 51 | 51 | 51 | 51 | 18 | 55 | 77 | 18 | 64 | 64 | 77 | 38 | 77 | 77 | 77 | 92 | 518 | 136 |
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.











