Surf Forecasts:
Mainside surf forecast from 18 Aug 2026:
- Most powerful swell: Wednesday 26 Aug, 3AM (local time) - 7.5ft (2.3m), 16s period, E swell with 2,633 kJ wave energy.
Best Forecast Surf Conditions for Mainside this week:
The most powerful waves expected at Mainside in the next 16 days are 2.3m 16s and forecast to arrive on Wednesday (Aug 26) at 3AM. Winds are predicted to be cross-shore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 5.0m 11s period and expected on Sunday (Aug 23) at 3AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 3AM (Wed 26th Aug) | 7.5ft (2.3m) 16s |
Table - best surf conditions forecast for Mainside over the next 16 days.
The Lowdown
Hey, it's Rusty. Let’s size it up. Mainside is looking pretty quiet for a long stretch, and the first week and a half is mostly a bust. You’ll be waiting until late August for anything worth paddling out for.
Starting Wednesday the 19th, we’ve got a small 4ft east swell with a short 7-second period. Wind is offshore, but the wave energy is weak (152) and the surf quality is poor. That’s the pattern for a while. From the 20th through the 25th, it’s nearly flat or tiny waves with zero energy recorded. Even when a little 5ft pulse shows on the 25th afternoon, the energy is only moderate (186) and conditions are still poor. Strong offshore winds don’t help when there’s nothing to ride.
Then things get heavy but ugly. The 26th and 27th have huge energy readings in the thousands, with swell heights up to 8ft from the east and north-northwest. But the wind turns into a gale and storm force cross-onshore, totally blowing everything out. That looks like a kite-surfing chaos, not a paddle session. The 28th and 29th are still big with strong onshore winds and lumpy conditions, so no thanks.
Now for the highlight. Sunday the 30th of August is what you’re waiting for. The morning brings a clean 6ft swell from the west-northwest with a 10-second period – that’s proper groundswell with solid energy (665). The wind goes glassy, and the report says “expect very good surf conditions.” The afternoon stays clean with a 5ft swell and light cross-off breezes. This is your window at Mainside. Water temp is a warm 83°F, about average for the time of year.
After that, it drops off into small, choppy waves from the 31st into September. There’s a small glimmer on September 2nd with a gentle offshore breeze and a 3ft east swell with a long 11-second period, giving you surfable but very ordinary waves. Energy is moderate (149). The afternoon goes glassy but still small.
So the bottom line is this: a long dry spell until Sunday the 30th of August. That’s your best bet, and it’s a good one – glassy conditions with a solid groundswell. Everything else is either flat or blown out.
Rusty.
Short Range ForecastHeavy rain (total 37mm), heaviest during Fri afternoon. Warm (max 28°C on Wed morning, min 26°C on Fri night). Mainly strong winds. | Days 4-6 Weather SummaryHeavy rain (total 25mm), heaviest during Sun night. Warm (max 28°C on Mon morning, min 26°C on Sat morning). Winds increasing (light winds from the E on Sat afternoon, near gales from the SE by Sun night). | ||||||||||||||||||||
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) | E 7 | E 7 | ESE 8 | ESE 8 | ESE 7 | ESE 7 | ESE 7 | E 9 | SE 10 | SE 9 | SSE 10 | SSE 10 | W 8 | W 7 | W 7 | ENE 13 | SSE 10 | E 7 | ESE 16 | ENE 7 | ESE 16 |
Wave Graph | |||||||||||||||||||||
152 | 139 | 0 | 0 | 0 | 0 | 0 | 24 | 0 | 0 | 0 | 0 | 10 | 4 | 4 | 16 | 0 | 210 | 0 | 186 | 0 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | off | off | off | off | off | off | cross-off | cross-off | cross-off | off | cross-off | off | off | off | off | off | off | cross-off | cross-off | cross |
High Tide | 11:19AM1.67m | 11:07PM1.91m | 12:19PM1.50m | 11:42PM1.80m | 2:15PM1.40m | 00:33AM1.69m | 5:17PM1.48m | 2:15AM1.61m | 6:02PM1.61m | 4:01AM1.63m | 6:26PM1.73m | 5:05AM1.73m | 6:47PM1.83m | ||||||||
Low Tide | 4:55PM0.98m | 6:04AM0.75m | 5:24PM1.15m | 7:13AM0.83m | 6:02PM1.32m | 8:53AM0.84m | 8:41PM1.43m | 10:25AM0.77m | 11:03PM1.37m | 11:21AM0.66m | 11:53PM1.25m | 12:00PM0.54m | 00:24AM1.12m | ||||||||
6:01 | — | — | 6:03 | — | — | 6:03 | — | — | 6:03 | — | — | 6:03 | — | — | 6:03 | — | — | 6:05 | — | — | |
— | 7:01 | — | — | 7:00 | — | — | 7:00 | — | — | 7:00 | — | — | 6:59 | — | — | 6:58 | — | — | 6:57 | — | |
mm | 1 | 1 | 3 | 4 | 3 | 5 | 4 | 5 | 11 | 3 | 2 | 8 | 1 | 5 | 6 | — | — | — | — | — | — |
Temp °C | 28 | 28 | 28 | 28 | 27 | 27 | 27 | 27 | 27 | 27 | 27 | 27 | 27 | 26 | 27 | 28 | 28 | 27 | 29 | 29 | 28 |
Feels °C | 29 | 29 | 29 | 29 | 28 | 28 | 29 | 29 | 31 | 25 | 30 | 28 | 24 | 21 | 25 | 25 | 26 | 26 | 30 | 30 | 29 |
Swell 1 Height (m) Direction Period (s) | SW 9 | SW 8 | S 9 | S 10 | S 9 | S 9 | S 9 | SSW 9 | SW 10 | SW 10 | SW 10 | SW 11 | SW 10 | SW 10 | SW 11 | SW 10 | SSE 10 | SSE 10 | ESE 16 | ESE 16 | ESE 16 |
19 | 11 | 13 | 45 | 78 | 74 | 74 | 199 | 181 | 281 | 240 | 258 | 177 | 180 | 137 | 87 | 391 | 230 | 1055 | 1358 | 2226 | |
Swell 2 Height (m) Direction Period (s) | S 8 | S 8 | SW 8 | SW 9 | SW 9 | SW 9 | SW 9 | ESE 7 | — | — | — | — | W 8 | W 7 | W 7 | W 8 | SW 10 | ESE 15 | SSE 9 | S 10 | SW 9 |
1 | 5 | 11 | 12 | 13 | 12 | 65 | 82 | — | — | — | — | 10 | 4 | 4 | 12 | 129 | 256 | 103 | 65 | 43 | |
Swell 3 Height (m) Direction Period (s) | SE 10 | — | — | — | — | — | — | E 9 | — | — | — | — | — | — | — | ENE 13 | ESE 16 | SW 10 | SW 10 | SW 10 | S 10 |
4 | — | — | — | — | — | — | 24 | — | — | — | — | — | — | — | 16 | 25 | 80 | 47 | 47 | 48 | |
Wind waves Height (m) Direction Period (s) | E 7 | E 7 | ESE 8 | ESE 8 | ESE 7 | ESE 7 | ESE 7 | — | SE 10 | SE 9 | SSE 10 | SSE 10 | SSE 10 | SSE 10 | SSE 10 | SSE 10 | E 5 | E 7 | ENE 5 | ENE 7 | NNE 5 |
152 | 139 | 143 | 209 | 168 | 128 | 282 | — | 1316 | 2007 | 2149 | 2811 | 2049 | 1255 | 1568 | 1138 | 92 | 210 | 109 | 186 | 47 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 650 | 9 | 14 | 608 | 14 | 14 | 14 | 600 | 608 | 608 | 10 | 600 | 600 | 622 | 600 | 633 | 830 | 608 | 13 | 650 | 618 |
Best forecast wave conditions in Okinawa | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
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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.











