Surf Forecasts:
Mainside surf forecast from 12 Sep 2026:
- Best quality surf: Friday 18 Sep, 3AM (local time) - 3ft (0.9m), 9s period, E swell with cross-offshore winds.
- Most powerful swell: Sunday 20 Sep, 9AM (local time) - 5.5ft (1.7m), 15s period, E swell with 1,212 kJ wave energy.
- Next surfable swell (1★+): Monday 14 Sep, 9PM (local time) - 2.5ft (0.7m), 9s period with E 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 Monday (Sep 14) at 9PM. The primary swell is predicted to be 0.7m and 9s 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 Mainside in the next 16 days are 1.7m 15s and forecast to arrive on Sunday (Sep 20) at 9AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.8m 8s period and expected on Monday (Sep 14) at 12AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Mon 14th Sep) | 2.5ft (0.7m) 9s |
| Best Surf | 3AM (Fri 18th Sep) | 3ft (0.9m) 9s |
| Most Powerful | 9AM (Sun 20th Sep) | 5.5ft (1.7m) 15s |
Table - best surf conditions forecast for Mainside over the next 16 days.
The Lowdown
Alright, let’s break it down in feet and Fahrenheit.
Yeah, I’m not gonna lie to you – the next 16 days at Mainside are looking mostly flat, messy, or just not worth paddling out for. We’ve got a long dry spell ahead.
The first real hint of something surfable shows up Tuesday morning, 15th September. Tiny waves, about 2 ft from the east, with a period of 9 seconds. The combined energy is still weak at 125, so it’s longboard or swim territory. The wind is light and cross-off from the ENE, so it’ll be clean, but it’s very ordinary.
Wednesday the 16th is much the same story – 2 ft, east swell, 10-second period, and clean conditions in the morning. Energy ticks up to 165, but it’s still not great. Thursday and Friday drop off even smaller, with energy under 100.
The real change comes around the weekend of the 19th and 20th September. The swell builds, but so does the wind. By Saturday afternoon the 19th, a long-period east groundswell comes in at 4 ft with a 16-second period, and energy jumps to 675. That’s got some push, but the wind is blowing cross-shore at 19 mph, making it lumpy. For a reef, that long period can make waves a bit straight, but there’s some power.
Sunday the 20th and Monday the 21st see the swell push over 5 ft, with energy over 1000, but the wind cranks up to 25 mph from the north and northwest. That’s strong cross-onshore to onshore – unsurfable for paddle surfing. Would be better for kite surfing.
The pattern stays poor through the end of the month. By the 27th and 28th September, waves hit 10 ft to 13 ft from the NNW, with energy in the thousands. But the wind is still strong and cross-shore, making it a lumpy, blown-out mess. That’s expert-only size, but the wind kills it.
The only real standout is Wednesday morning, 16th September. The swell is tiny at 2 ft from the east, but the wind is light and cross-off, so Mainside reef will be clean. It’s the cleanest window in a bleak outlook.
Water temp is about 84°F, which is average for this time of year.
First week is tiny, second week is too big and windy. It’s a rough run, but that can change. Keep watching the wind.
Rusty.
Short Range ForecastModerate rain (total 14mm), heaviest on Sun afternoon. Warm (max 29°C on Sun morning, min 27°C on Sun morning). Wind will be generally light. | Days 4-6 Weather SummaryModerate rain (total 18mm), heaviest on Fri afternoon. Warm (max 28°C on Wed morning, min 27°C on Wed morning). Wind will be generally light. | ||||||||||||||||||||
Sunday 13 | Monday 14 | Tuesday 15 | Wednesday 16 | Thursday 17 | Friday 18 | Saturday 19 | |||||||||||||||
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 14 | E 14 | E 13 | E 13 | E 13 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | NNW 7 | ENE 14 | E 9 | ENE 13 | ENE 12 | ENE 12 | E 8 | N 8 | E 16 | E 16 |
Wave Graph  | |||||||||||||||||||||
 kJ | 35 | 36 | 32 | 31 | 14 | 78 | 81 | 88 | 87 | 90 | 65 | 63 | 38 | 41 | 34 | 30 | 29 | 22 | 45 | 628 | 1101 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross | cross | cross-on |
High Tide | 8:30PM2.17m | 8:56AM2.10m | 8:54PM2.14m | 9:30AM1.97m | 9:19PM2.09m | 10:06AM1.82m | 9:44PM2.01m | 10:45AM1.67m | 10:10PM1.90m | 11:36AM1.52m | 10:38PM1.77m | 1:12PM1.41m | 11:17PM1.63m | ||||||||
Low Tide | 2:29PM0.49m | 2:47AM0.36m | 2:56PM0.61m | 3:19AM0.37m | 3:20PM0.75m | 3:52AM0.44m | 3:44PM0.89m | 4:28AM0.53m | 4:08PM1.03m | 5:09AM0.65m | 4:32PM1.18m | 6:06AM0.76m | 5:06PM1.32m | ||||||||
 |  |  | | | | |  |  | | | | | | | | | | | | | |
 | 6:13 | — | — | 6:13 | — | — | 6:13 | — | — | 6:13 | — | — | 6:15 | — | — | 6:15 | — | — | 6:15 | — | — |
 | — | 6:36 | — | — | 6:35 | — | — | 6:34 | — | — | 6:32 | — | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — |
mm | — | 3 | 3 | 1 | 2 | 3 | 2 | — | — | 1 | 2 | 2 | 2 | 2 | — | 1 | 8 | — | — | — | — |
Temp °C | 29 | 29 | 27 | 28 | 28 | 27 | 28 | 28 | 27 | 28 | 28 | 27 | 28 | 28 | 27 | 28 | 28 | 27 | 28 | 28 | 27 |
Feels °C | 31 | 31 | 30 | 32 | 31 | 30 | 32 | 30 | 29 | 32 | 31 | 30 | 32 | 31 | 30 | 31 | 30 | 29 | 29 | 28 | 27 |
Swell 1 Height (m) Direction Period (s) | NNW 6 | ESE 7 | N 5 | ESE 8 | ESE 9 | E 9 | E 9 | E 10 | E 10 | E 10 | NNW 7 | NNW 7 | NNW 6 | N 6 | N 7 | E 9 | E 9 | E 8 | E 18 | E 16 | E 16 |
| kJ | 12 | 29 | 13 | 75 | 79 | 78 | 81 | 88 | 87 | 90 | 61 | 53 | 23 | 18 | 24 | 38 | 38 | 22 | 156 | 628 | 1101 |
Swell 2 Height (m) Direction Period (s) | E 14 | E 14 | E 13 | N 5 | N 5 | E 13 | NNW 6 | NNW 6 | NNW 6 | NNW 6 | E 10 | E 9 | E 9 | E 9 | ESE 9 | N 7 | N 7 | N 6 | E 8 | E 8 | N 9 |
| kJ | 35 | 36 | 32 | 4 | 2 | 31 | 16 | 13 | 20 | 36 | 65 | 63 | 42 | 41 | 26 | 23 | 24 | 7 | 20 | 35 | 6 |
Swell 3 Height (m) Direction Period (s) | ESE 9 | NNW 6 | S 6 | E 13 | E 13 | N 5 | E 13 | E 12 | SW 8 | ENE 14 | ENE 14 | ENE 14 | ENE 14 | ENE 13 | ENE 13 | ENE 12 | ENE 12 | ENE 12 | ENE 11 | S 8 | S 8 |
| kJ | 17 | 3 | 1 | 31 | 14 | 2 | 28 | 12 | 2 | 39 | 37 | 40 | 38 | 34 | 34 | 30 | 29 | 14 | 13 | 5 | 5 |
Wind waves Height (m) Direction Period (s) | E 5 | NE 3 | ESE 8 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | ENE 2 | N 8 | N 4 | N 5 |
| kJ | 21 | 9 | 85 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 45 | 12 | 70 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 13 | 13 | 600 | 25 | 25 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 13 | 13 | 650 | 980 | 608 |
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.
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