
Surf Forecasts:
Rock Island surf forecast from 6 Aug 2026:
- Best quality surf: Sunday 9 Aug, 9AM (local time) - 2.5ft (0.7m), 10s period, S swell with cross-offshore winds.
- Most powerful swell: Thursday 6 Aug, 9PM (local time) - 6ft (1.9m), 14s period, S swell with 1,352 kJ wave energy.
- Next surfable swell (1★+): Sunday 9 Aug, 9AM (local time) - 2.5ft (0.7m), 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 Sunday (Aug 09) at 9AM. The primary swell is predicted to be 0.7m and 10s period with a secondary swell of 0.3m and 13s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Rock Island in the next 16 days are 1.9m 14s and forecast to arrive on Thursday (Aug 06) at 9PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 3s period and expected on Tuesday (Aug 11) at 9PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9AM (Sun 9th Aug) | 2.5ft (0.7m) 10s |
| Best Surf | 9AM (Sun 9th Aug) | 2.5ft (0.7m) 10s |
| Most Powerful | 9PM (Thu 6th Aug) | 6ft (1.9m) 14s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s talk about what’s happening at Rock Island.
Right off the bat, we’ve got a bit of a tease. The forecast kicks off on Thursday, August 6th with a solid 6ft swell from the SSE, period hanging at a solid 13 seconds, and the combined energy is strong at 1131. That’s proper groundswell energy. But – and this is a big but – the wind is cross-offshore from the NE in the morning, so it’s clean, but the wave comment is "marginal," and the tide’s not playing ball. By the afternoon, it swings onshore from the S. This swell has real potential for a reef like Rock Island, but you’d have to be picky about the tide window. The water’s sitting at 82°, which is a touch warmer than normal for this time of year – about 2° above average, so it’s noticeably warm.
Friday, August 7th, the swell drops to 5ft, period still good at 13 seconds, but the wind is a light cross-on from the SSE in the morning, putting small ripples on the face. The energy is still chunky at 974 (moderate). Afternoon turns into a complete write-off with onshore wind and poor conditions. Saturday, August 8th, the swell fades to 4ft, period drops to 11 seconds, and the morning is cross-on with a slight air. The energy is down to 368 (moderate). This isn’t worth getting wet for.
Sunday, August 9th, the swell is tiny, 2ft, period 10 seconds, but the morning is glassy. That’s the only clean moment, but the wave energy is weak at 172. It’s surfable, but very ordinary. Then from Monday, August 10th, through Sunday, August 16th, it’s a flat spell. Swell consistently below 2ft, periods dropping, energy in the 30s to 120s – weak. The wind is often offshore or cross-off, but there’s just no power. You’re looking at a solid 6-7 day gap of nothing worth paddling out for.
The second week isn’t much better. From Monday, August 17th, through to Friday, August 21st, the swell stays below 2ft. There’s a tiny blip of energy on Wednesday, August 19th, with a 1ft, 15-second period swell from the S – that’s a very long period, but it’s just too small. The combined energy is only 63. By Friday, August 21st, we see a slight uptick to 2ft from the S, period 12 seconds, and clean cross-off wind in the afternoon, with energy climbing to 111. That’s weak energy, but it’s the best of the second week. Still, it’s marginal.
Overall, the standout window is the morning of Thursday, August 6th. That’s your best bet – 6ft, long period, clean cross-off wind, and strong energy. But it’s a short window, and you’ll have to work the tide. After that, it’s a long dry spell until the very end of the forecast, which is still too small to get excited about.
-Rusty
Short Range ForecastMostly dry. Warm (max 29°C on Thu afternoon, min 25°C on Sat night). Wind will be generally light. | Days 5-7 Weather SummaryMostly dry. Warm (max 30°C on Mon afternoon, min 24°C on Tue night). Mainly fresh winds. | |||||||||||||||||||
Thu 6 | Friday 7 | Saturday 8 | Sunday 9 | Monday 10 | Tuesday 11 | Wednesday 12 | ||||||||||||||
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 13 | S 14 | S 13 | S 12 | S 11 | S 11 | S 11 | SSW 11 | S 10 | S 11 | S 10 | SSW 11 | SSW 11 | SSW 10 | SSW 11 | SSW 11 | SSW 11 | SSW 11 | SSW 11 | SW 11 |
Wave Graph | ||||||||||||||||||||
1053 | 1294 | 810 | 625 | 426 | 302 | 247 | 198 | 102 | 82 | 78 | 93 | 88 | 62 | 70 | 69 | 71 | 70 | 47 | 21 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-on | cross-on | on | cross-on | on | on | on | cross-off | on | cross-off | off | cross-off | off | off | cross-off | off | cross | on | off |
High Tide | 9:49PM1.41m | 12:41PM1.13m | 10:30PM1.40m | 2:57PM1.19m | 11:28PM1.38m | 4:09PM1.28m | 00:45AM1.38m | 4:47PM1.36m | 2:03AM1.40m | 5:17PM1.41m | 3:09AM1.45m | 5:43PM1.45m | ||||||||
Low Tide | 3:39PM0.90m | 5:21AM0.46m | 4:23PM1.04m | 6:37AM0.41m | 5:47PM1.15m | 7:52AM0.33m | 7:53PM1.19m | 8:54AM0.25m | 9:16PM1.16m | 9:46AM0.18m | 10:08PM1.08m | 10:31AM0.14m | 10:48PM0.99m | |||||||
— | — | 4:54 | — | — | 4:54 | — | — | 4:54 | — | — | 4:56 | — | — | 4:56 | — | — | 4:58 | — | — | |
6:40 | — | — | 6:39 | — | — | 6:38 | — | — | 6:37 | — | — | 6:37 | — | — | 6:36 | — | — | 6:35 | — | |
mm | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 7 |
Temp °C | 29 | 27 | 28 | 28 | 27 | 27 | 28 | 26 | 28 | 28 | 26 | 29 | 30 | 26 | 28 | 29 | 25 | 27 | 27 | 26 |
Feels °C | 32 | 30 | 30 | 29 | 30 | 30 | 29 | 28 | 31 | 28 | 28 | 27 | 28 | 23 | 26 | 27 | 23 | 29 | 27 | 28 |
Swell 1 Height (m) Direction Period (s) | S 13 | S 14 | S 13 | S 12 | S 11 | S 11 | S 11 | SSW 11 | S 10 | S 11 | S 10 | SSW 11 | SSW 11 | SSW 10 | SSW 11 | SSW 11 | SSW 11 | SSW 11 | SSW 11 | SSW 10 |
1053 | 1294 | 810 | 625 | 426 | 302 | 247 | 198 | 102 | 82 | 78 | 93 | 88 | 62 | 70 | 69 | 71 | 70 | 47 | 21 | |
Swell 2 Height (m) Direction Period (s) | ESE 11 | ESE 10 | ESE 9 | SE 9 | SE 12 | ESE 11 | ESE 12 | ESE 12 | ESE 13 | ESE 13 | ESE 12 | ESE 12 | ESE 11 | ESE 11 | SW 12 | SE 13 | SE 13 | SE 12 | ESE 11 | SW 11 |
11 | 114 | 148 | 192 | 6 | 11 | 13 | 30 | 34 | 34 | 15 | 14 | 12 | 12 | 6 | 6 | 7 | 5 | 11 | 20 | |
Swell 3 Height (m) Direction Period (s) | — | — | E 15 | SE 9 | E 15 | SE 12 | SE 12 | SE 12 | SW 12 | SW 12 | SW 12 | SE 11 | SE 11 | SE 14 | SE 12 | SW 12 | E 10 | S 10 | S 10 | ESE 11 |
— | — | 4 | 21 | 4 | 6 | 6 | 5 | 21 | 6 | 23 | 4 | 5 | 7 | 6 | 6 | 2 | 2 | 2 | 11 | |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | S 2 | — | — | — | — | — | — | NE 2 | NNE 3 | ENE 3 | NE 3 | NE 3 | NE 3 | NE 3 |
— | — | — | — | — | — | 1 | — | — | — | — | — | — | 1 | 3 | 4 | 5 | 3 | 2 | 5 | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 38 | 14 | 64 | 64 | 64 | 6 | 54 | 14 | 0 | 51 | 2 | 0 | 12 | 38 | 145 | 470 | 0 | 0 | 51 | 0 |
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.











