Surf Forecasts:
Rock Island surf forecast from 19 Aug 2026:
- Best quality surf: Monday 24 Aug, 9AM (local time) - 2.5ft (0.7m), 15s period, SE swell with cross-offshore winds.
- Most powerful swell: Wednesday 26 Aug, 3PM (local time) - 7ft (2.1m), 16s period, S swell with 2,206 kJ wave energy.
- Next surfable swell (1★+): Saturday 22 Aug, 9PM (local time) - 1.5ft (0.4m), 9s 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 Saturday (Aug 22) at 9PM. The primary swell is predicted to be 0.4m and 9s period with a secondary swell of 0.1m and 10s. Another secondary swell of 0.6m and 4s 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 2.1m 16s and forecast to arrive on Wednesday (Aug 26) at 3PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.3m 3s period and expected on Sunday (Aug 23) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Sat 22nd Aug) | 1.5ft (0.4m) 9s |
| Best Surf | 9AM (Mon 24th Aug) | 2.5ft (0.7m) 15s |
| Most Powerful | 3PM (Wed 26th Aug) | 7ft (2.1m) 16s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s check out what Rock Island’s got.
Honestly, the first few days are a total bust. From Wednesday the 19th through Sunday the 23rd, we’ve got barely a ripple—swell heights staying under 3 feet and wind blowing onshore or cross-on. Not worth wetting your wetsuit for. Water temp is a normal 80°, no big deal.
The first real glimmer comes Monday morning the 24th. A long period groundswell from the SE at 2 feet with a 15-second period shows up. Energy is moderate (228). It’s glassy, clean, with a light cross-off breeze. This will be a fun little tide for beginners or anyone wanting a cruisey session. The reef should handle it well since the swell direction is close to the optimum S.
The swell picks up later in the week, but the wind gets ugly. The real standout is Monday morning the 31st of August. You’re looking at a 5-foot SSE groundswell with a 16-second period—long period means proper, powerful waves, best suited for a reef like Rock Island. The wind is a fresh offshore from the NNE at 15 mph, keeping the surface buttery. The energy is strong at 2259. That’s the session to aim for. It’s a week and a half out, so keep your fingers crossed, but it’s the best bet of this whole outlook.
- Rusty
Short Range ForecastMostly dry. Warm (max 27°C on Wed morning, min 25°C on Wed night). Wind will be generally light. | Days 4-6 Weather SummaryLight rain (total 6mm), mostly falling on Sat night. Warm (max 28°C on Sat morning, min 24°C on Sat night). Wind will be generally light. | ||||||||||||||||||||
Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | |||||||||||||||
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) | SE 6 | SSE 6 | SSW 8 | SSE 6 | SSW 9 | S 10 | SSW 9 | S 9 | SSW 9 | SSW 9 | SSW 9 | SW 9 | SSW 9 | SE 13 | SE 12 | SE 15 | SSE 14 | SSE 15 | SSE 15 | SSE 14 | SSE 13 |
Wave Graph  | |||||||||||||||||||||
 kJ | 10 | 7 | 6 | 4 | 8 | 8 | 27 | 101 | 124 | 32 | 108 | 21 | 15 | 27 | 37 | 217 | 325 | 656 | 996 | 1031 | 663 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | on | on | cross-on | on | on | on | on | on | on | on | off | off | glassy | glassy | cross-off | on | on | on | on | on |
High Tide | 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 | 4:17PM1.34m | 1:21AM1.36m | 4:45PM1.39m | 2:39AM1.41m | ||||||||
Low Tide | 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 | 8:12AM0.33m | 8:44PM1.17m | 9:11AM0.27m | 9:41PM1.08m | ||||||||
 | |  | |  | |  | | | | |  | | |  | | | | | | | |
 | 5:03 | — | — | 5:03 | — | — | 5:05 | — | — | 5:05 | — | — | 5:05 | — | — | 5:07 | — | — | 5:07 | — | — |
 | — | 6:27 | — | — | 6:24 | — | — | 6:23 | — | — | 6:22 | — | — | 6:22 | — | — | 6:20 | — | — | 6:19 | — |
mm | — | — | — | — | — | — | — | — | — | — | — | 6 | — | — | — | — | — | — | — | — | — |
Temp °C | 27 | 27 | 26 | 27 | 27 | 26 | 27 | 27 | 27 | 28 | 28 | 28 | 26 | 27 | 26 | 26 | 27 | 26 | 27 | 27 | 27 |
Feels °C | 30 | 28 | 28 | 29 | 28 | 28 | 28 | 27 | 28 | 30 | 29 | 33 | 29 | 30 | 29 | 30 | 29 | 28 | 29 | 28 | 27 |
Swell 1 Height (m) Direction Period (s) | SE 6 | SE 10 | SSE 6 | SSE 6 | SSW 9 | SSW 8 | SSW 9 | SE 11 | SE 10 | SSW 9 | SE 10 | S 4 | SSW 9 | SSW 9 | SSW 9 | SE 15 | SSE 14 | SSE 15 | SSE 15 | SSE 14 | SSE 13 |
| kJ | 10 | 4 | 3 | 3 | 8 | 6 | 27 | 4 | 4 | 32 | 4 | 9 | 15 | 15 | 25 | 217 | 325 | 656 | 996 | 1031 | 663 |
Swell 2 Height (m) Direction Period (s) | SE 10 | SW 8 | SE 10 | SE 10 | SSE 6 | S 10 | SE 11 | S 9 | S 9 | SE 10 | SE 11 | SW 9 | S 4 | SE 13 | SE 12 | SSW 8 | SSW 10 | SSE 18 | SSW 10 | SSW 10 | S 16 |
| kJ | 4 | 3 | 4 | 4 | 3 | 8 | 4 | 2 | 2 | 4 | 5 | 21 | 1 | 27 | 37 | 7 | 11 | 266 | 10 | 10 | 526 |
Swell 3 Height (m) Direction Period (s) | SSW 8 | SW 9 | SSW 8 | SW 8 | SE 11 | SE 11 | S 13 | S 9 | SE 5 | SE 11 | SSE 10 | SE 10 | SE 10 | — | SSE 14 | SW 11 | ESE 12 | SW 10 | ESE 14 | ESE 13 | SSW 10 |
| kJ | 6 | 3 | 6 | 2 | 4 | 4 | 3 | 2 | 1 | 5 | 10 | 4 | 4 | — | 21 | 4 | 28 | 54 | 37 | 58 | 10 |
Wind waves Height (m) Direction Period (s) | — | SSE 6 | — | — | S 2 | SSE 5 | S 3 | S 9 | SSW 9 | SSW 4 | SSW 9 | SSW 4 | NE 2 | SSE 4 | — | — | SSW 8 | — | — | — | — |
| kJ | — | 7 | — | — | 1 | 6 | 1 | 101 | 124 | 6 | 108 | 9 | 1 | 2 | — | — | 12 | — | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 77 | 77 | 54 | 77 | 77 | 76 | 76 | 77 | 14 | 90 | 491 | 16 | 51 | 16 | 0 | 0 | 18 | 14 | 18 | 77 | 27 |
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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