Surf Forecasts:
Mainside surf forecast from 16 Sep 2026:
- Best quality surf: Friday 18 Sep, 12AM (local time) - 2ft (0.6m), 8s period, N swell with cross-offshore winds.
- Most powerful swell: Sunday 20 Sep, 12AM (local time) - 3.5ft (1.1m), 13s period, E swell with 404 kJ wave energy.
- Next surfable swell (1★+): Friday 18 Sep, 12AM (local time) - 2ft (0.6m), 8s period with N swell.
Best Forecast Surf Conditions for Mainside this week:
The surf forecast for Mainside over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Friday (Sep 18) at 12AM. The primary swell is predicted to be 0.6m and 8s period with a secondary swell of 0.4m and 9s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Mainside in the next 16 days are 1.1m 13s and forecast to arrive on Sunday (Sep 20) at 12AM. Winds are predicted to be cross-shore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.5m 9s period and expected on Thursday (Sep 17) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12AM (Fri 18th Sep) | 2ft (0.6m) 8s |
| Best Surf | 12AM (Fri 18th Sep) | 2ft (0.6m) 8s |
| Most Powerful | 12AM (Sun 20th Sep) | 3.5ft (1.1m) 13s |
Table - best surf conditions forecast for Mainside over the next 16 days.
The Lowdown
Alright folks, let's be straight up. Mainside has been a total no-go for a while, and it's gonna stay that way for the next week and a half. We're looking at a big dry spell with next to no waves from now until the end of the month. The first real chance for a wave doesn't pop up until the very end of the forecast period.
Right now and through the middle of September, the swell is weak. The wave energy is barely there (169), and the wind is a messy cross or cross-off breeze. Nothing worth getting wet for. The flat period really sets in from the 24th to the 26th, with energy numbers dropping to zero. It's a proper dead zone.
But then, things get interesting. On the 27th of September, a big swell starts to fill in. By the 28th, Monday morning, we're talking about a massive 18-foot wave from the WNW. The energy reading is a whopping 9133, which is super strong. The wind is a clean offshore from the ESE at 18 mph, which is perfect. But, and this is a big but, at that size, it's for expert surfers only. The period is 10 seconds, so it'll have decent shape, but it's going to be a freight train.
For the real standout, if you're an experienced surfer who knows the reef, the best window is Monday the 28th of September. Mainside is an exposed reef, so it'll handle that size, and with that clean offshore wind, it'll be absolutely firing. It'll be big, powerful, and demanding, but the quality will be there for those who can handle it. Just know that crowds are possible out there. The water temp is around 84°, which is normal for the time of year.
Keep in mind, that call for the 28th is promising but a long way out, so don't book the time off just yet. The days before and after, on the 27th and 29th, still have surfable waves, but the wind is stronger and conditions are messier. Hold the line, the wait might just be worth it.
Rusty.
Short Range ForecastLight rain (total 3mm), mostly falling on Wed morning. Warm (max 28°C on Fri morning, min 26°C on Wed morning). Wind will be generally light. | Days 4-6 Weather SummaryLight rain (total 4mm), mostly falling on Sat night. Warm (max 27°C on Sat morning, min 26°C on Sun night). Mainly fresh winds. | ||||||||||||||||||||
Wednesday 16 | Thursday 17 | Friday 18 | Saturday 19 | Sunday 20 | Monday 21 | Tuesday 22 | |||||||||||||||
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) | E 10 | NNW 7 | N 7 | E 9 | E 9 | N 8 | N 7 | E 9 | N 9 | N 9 | E 15 | E 13 | E 12 | E 12 | E 12 | ENE 12 | N 8 | N 8 | N 7 | N 7 | N 7 |
Wave Graph  | |||||||||||||||||||||
 kJ | 90 | 62 | 72 | 41 | 41 | 41 | 38 | 24 | 7 | 38 | 109 | 404 | 344 | 377 | 304 | 254 | 185 | 117 | 67 | 44 | 33 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | cross | cross-off | cross | cross | cross-off | cross-off | cross | cross-off | cross | cross | cross | cross | cross | cross | cross | cross-on | cross | cross | cross-on | glassy |
High Tide | 10:06AM1.82m | 9:44PM2.01m | 10:45AM1.67m | 10:10PM1.90m | 11:36AM1.52m | 10:38PM1.77m | 1:12PM1.41m | 11:17PM1.63m | 4:27PM1.47m | 1:01AM1.51m | 5:12PM1.60m | 3:33AM1.53m | 5:37PM1.72m | ||||||||
Low Tide | 3:44PM0.89m | 4:28AM0.53m | 4:08PM1.03m | 5:09AM0.65m | 4:32PM1.18m | 6:06AM0.76m | 5:06PM1.32m | 7:38AM0.84m | 8:16PM1.42m | 9:28AM0.81m | 10:42PM1.30m | 10:37AM0.71m | 11:24PM1.13m | ||||||||
 | |  |  | | | | | | | |  |  | | |  | |  | | | | |
 | 6:13 | — | — | 6:15 | — | — | 6:15 | — | — | 6:15 | — | — | 6:16 | — | — | 6:16 | — | — | 6:16 | — | — |
 | — | 6:32 | — | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — | — | 6:28 | — | — | 6:27 | — | — | 6:25 | — |
mm | 1 | 1 | — | — | 1 | — | — | — | — | — | — | 1 | 1 | 1 | 1 | — | — | — | — | — | — |
Temp °C | 27 | 27 | 26 | 27 | 27 | 27 | 28 | 28 | 27 | 27 | 27 | 27 | 27 | 27 | 26 | 27 | 27 | 27 | 26 | 26 | 26 |
Feels °C | 29 | 28 | 27 | 29 | 29 | 30 | 32 | 30 | 30 | 29 | 28 | 28 | 28 | 28 | 24 | 25 | 25 | 26 | 25 | 26 | 27 |
Swell 1 Height (m) Direction Period (s) | NNW 6 | NNW 7 | E 9 | E 9 | N 6 | N 8 | N 7 | N 7 | ESE 9 | N 9 | E 15 | E 13 | E 12 | E 12 | E 12 | ENE 12 | N 8 | N 8 | N 7 | N 7 | N 7 |
| kJ | 39 | 62 | 61 | 41 | 19 | 41 | 38 | 23 | 29 | 38 | 109 | 404 | 344 | 377 | 304 | 254 | 185 | 117 | 67 | 44 | 33 |
Swell 2 Height (m) Direction Period (s) | E 10 | E 9 | ENE 14 | ENE 14 | E 9 | E 9 | E 9 | E 9 | N 6 | ESE 10 | ESE 10 | N 8 | N 7 | S 8 | S 8 | S 8 | ENE 12 | ENE 11 | ENE 11 | ENE 11 | ENE 10 |
| kJ | 90 | 62 | 40 | 38 | 41 | 24 | 25 | 24 | 7 | 31 | 31 | 49 | 15 | 5 | 5 | 5 | 140 | 68 | 23 | 11 | 9 |
Swell 3 Height (m) Direction Period (s) | ENE 14 | ENE 14 | SE 9 | SE 9 | ENE 13 | ENE 13 | ENE 12 | ENE 12 | N 9 | ENE 11 | NE 11 | S 8 | NW 4 | SE 9 | — | SE 10 | S 8 | S 7 | SE 9 | E 10 | E 9 |
| kJ | 40 | 37 | 3 | 3 | 34 | 34 | 30 | 14 | 6 | 25 | 31 | 6 | 3 | 3 | — | 4 | 5 | 1 | 3 | 2 | 2 |
Wind waves Height (m) Direction Period (s) | — | — | N 7 | N 6 | — | NNE 2 | — | — | N 3 | — | N 7 | N 8 | NNE 3 | N 6 | N 8 | N 8 | — | — | — | — | — |
| kJ | — | — | 72 | 41 | — | 1 | — | — | 3 | — | 24 | 37 | 4 | 28 | 122 | 186 | — | — | — | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 10 | 13 | 10 | 10 | 0 | 0 | 13 | 36 | 36 | 650 | 9 | 27 | 36 | 608 | 608 | 660 | 1 | 1 | 27 | 29 |
Best forecast wave conditions in Okinawa | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
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The surf report / weather widget below is available to embed on third party websites free of charge and provides a summary of our Mainside 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 Mainside Surf forecast
The above surf forecast table for Mainside provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Mainside can be found by selecting the local surf guide option on the grey menu. Our Mainside 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 (Mainside) 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 Mainside 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.
Mainside is 11 km (7 miles) from the city of Ishikawa. If you plan a holiday in Okinawa, look for hotels and other accommodation in Ishikawa. Ishikawa has rooms for a wide range of budgets as well as car hire and transport links.
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