Surf Forecasts:
Rock Island surf forecast from 17 Aug 2026:
- Most powerful swell: Friday 21 Aug, 6PM (local time) - 2.5ft (0.8m), 9s period, S swell with 99 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 0.8m 9s and forecast to arrive on Friday (Aug 21) at 6PM. 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 | 6PM (Fri 21st Aug) | 2.5ft (0.8m) 9s |
Table - best surf conditions forecast for Rock Island over the next 16 days.
The Lowdown
Alright, Rusty here, and it's a slow start for the next week or so. Rock Island is showing tiny surf through the 24th, with waves barely getting to 2 feet and a persistent onshore breeze messing up the surface. The water's warm, feeling normal for this time of year at about 81.3°. Nothing worth getting wet for just yet, but hold tight.
We finally see some life on the 25th. Tuesday morning brings a 3.3ft groundswell from the SSE with a long 14-second period and some real energy behind it (502). That's a proper swell pulse coming through, but the wind is straight onshore, so it's a bit of a tease. The swell builds nicely through the rest of the week, pushing up to about 6.2ft on the 28th, but onshore winds keep it from being clean.
The main event is the final day of August. Sunday the 31st fires up with a big 10-foot S swell, a very long 17-18 second period, and massive energy readings (6698). That's a powerful, deep-ocean groundswell. The wind is going to be siding across it, keeping things a bit choppy. For experienced surfers, that's serious, powerful surf, but with waves over 8 feet, it's an expert-only zone. Beginners, sit this one out.
As we hit September 1st, we're still looking at solid 8-foot S swells with long periods. The wind is trying to lighten up on that first morning, which could offer the cleanest look at some big, strong waves. It’s promising, but we'll see how it lines up.
Short Range ForecastMostly dry. 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 25°C on Thu night). Wind will be generally light. | ||||||||||||||||||||
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 | SSE 6 | SSW 8 | SSE 6 | SSW 9 | SSW 10 | S 9 | S 9 | SSW 10 | SSW 10 | SSW 10 | SSW 9 | SSW 9 | SSW 9 | S 9 |
Wave Graph  | |||||||||||||||||||||
 kJ | 23 | 14 | 7 | 6 | 12 | 11 | 6 | 7 | 6 | 4 | 8 | 32 | 41 | 74 | 42 | 57 | 55 | 35 | 48 | 28 | 41 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | on | cross | glassy | on | cross-on | cross-off | on | cross-on | cross | 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 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 27 | 28 | 26 | 26 | 27 | 26 | 27 | 28 | 26 | 27 | 27 | 26 | 27 | 27 | 26 | 27 | 27 | 27 | 27 | 27 | 27 |
Feels °C | 31 | 30 | 29 | 30 | 28 | 29 | 30 | 30 | 29 | 29 | 28 | 28 | 28 | 27 | 26 | 30 | 28 | 28 | 29 | 25 | 27 |
Swell 1 Height (m) Direction Period (s) | S 9 | SSW 8 | SSE 6 | SSE 6 | SSW 8 | SE 7 | SE 6 | SE 10 | SSE 6 | SSE 6 | SSW 9 | SSW 10 | S 9 | SE 10 | SSW 10 | SSW 10 | SSW 10 | SSW 9 | SSW 9 | SSW 9 | S 9 |
| kJ | 23 | 14 | 3 | 3 | 6 | 11 | 6 | 4 | 3 | 3 | 8 | 32 | 41 | 4 | 42 | 57 | 55 | 35 | 48 | 28 | 41 |
Swell 2 Height (m) Direction Period (s) | SE 11 | SE 11 | SSW 8 | SSW 8 | SE 10 | SSW 8 | SE 10 | SW 8 | SE 10 | SE 10 | SSE 6 | SSE 6 | ESE 11 | — | SSW 8 | SE 10 | SE 10 | SE 10 | SSE 10 | SSE 10 | SE 11 |
| kJ | 5 | 4 | 7 | 6 | 4 | 6 | 4 | 3 | 4 | 4 | 3 | 3 | 11 | — | 23 | 4 | 4 | 4 | 10 | 9 | 5 |
Swell 3 Height (m) Direction Period (s) | E 9 | E 8 | SE 10 | SE 10 | SSW 8 | SE 10 | SW 8 | SE 6 | SSW 8 | SW 8 | SE 11 | SE 11 | S 9 | E 9 | SE 10 | SE 11 | SE 11 | SE 11 | SE 11 | SE 11 | SE 9 |
| kJ | 1 | 1 | 4 | 4 | 12 | 4 | 2 | 2 | 6 | 2 | 4 | 4 | 2 | 1 | 4 | 5 | 5 | 4 | 4 | 5 | 3 |
Wind waves Height (m) Direction Period (s) | — | SSE 5 | — | — | SSE 6 | — | — | SSE 6 | — | — | S 2 | — | SE 7 | S 9 | S 4 | SSW 4 | S 4 | S 4 | — | — | — |
| kJ | — | 3 | — | — | 8 | — | — | 7 | — | — | 1 | — | 16 | 74 | 9 | 5 | 9 | 7 | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 51 | 51 | 51 | 51 | 18 | 51 | 74 | 18 | 77 | 77 | 77 | 54 | 64 | 77 | 14 | 92 | 77 | 38 | 92 | 77 | 92 |
Best forecast wave conditions in Kanagawa | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
Header Global | |||||||||||||||||||||
- Map Icons:
Break
Live Wave Height (m)
Live Wind Speed (km/h)
Surf Rating (10 Max)
Ocean Swells (m)- Wind Speed (km/h)
FREE! Surf-Forecast.com widget for your website
The surf report / weather widget below is available to embed on third party websites free of charge and provides a summary of our Rock Island surf forecast. Simply grab the html code snippet that we provide and paste it into your own site. You can choose your preferred language and metric/imperial units for the surf forecast feed to suit users of your site. Click here to get the code.
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.
Nearest