Surf Forecasts:
Onjuku surf forecast from 25 Aug 2026:
- Best quality surf: Thursday 27 Aug, 3PM (local time) - 2.5ft (0.7m), 13s period, E swell with cross-offshore winds.
- Most powerful swell: Tuesday 25 Aug, 3PM (local time) - 5ft (1.6m), 12s period, SSE swell with 658 kJ wave energy.
- Next surfable swell (1★+): Thursday 27 Aug, 3PM (local time) - 2.5ft (0.7m), 13s period with E swell.
Best Forecast Surf Conditions for Onjuku this week:
The surf forecast for Onjuku over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Thursday (Aug 27) at 3PM. The primary swell is predicted to be 0.7m and 13s period with a secondary swell of 0.8m and 6s. Another secondary swell of 1.3m and 6s is also forecast. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Onjuku in the next 16 days are 1.6m 12s and forecast to arrive on Tuesday (Aug 25) 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 0.8m 4s period and expected on Saturday (Aug 29) at 12PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3PM (Thu 27th Aug) | 2.5ft (0.7m) 13s |
| Best Surf | 3PM (Thu 27th Aug) | 2.5ft (0.7m) 13s |
| Most Powerful | 3PM (Tue 25th Aug) | 5ft (1.6m) 12s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let’s look at what’s lining up for Onjuku over the next couple of weeks.
Right off the bat, we’ve got a bit of a rough patch. The first few days are a write-off. Tuesday the 25th and Wednesday the 26th have some solid swell size, but that cross-onshore wind has got it all chopped up and messy. Not worth paddling out for. Thursday the 27th morning is still a mess with a storm risk, but the afternoon throws us a little bone. The wind shifts to a cross-offshore, and the conditions clean right up.
The real standout window doesn’t arrive until Sunday the 6th of September. That morning, the stars align. We’ve got a 5ft swell from the SSE, with a nice long 12-second period. That’s proper groundswell energy, and the water is a touch warmer than normal for this time of year, sitting at 82°. The combined energy is a solid 855 (moderate to strong) – you’ll feel that push. The wind is a gentle cross-offshore breeze, keeping the surface clean. This is the best on offer. It’s a consistent-enough spot, but don’t expect it to be empty; crowds are possible.
Monday the 7th of September keeps the swell going, pushing up to 7ft in the morning and 8ft in the afternoon from the SE. That’s getting up there in size – better for the more experienced crew. The wind stays clean and cross-off, but the period drops to 9 seconds, so it’s a bit more local windswell mixed in. Still, some solid waves to be had.
Tuesday the 8th of September morning is another standout. The swell drops back to 6ft from the S, with an 8-second period, but the wind is gentle and cross-off, and the energy is still strong at 662. The conditions are clean, and it’s a good day for a paddle.
The first week of September looks better than the rest, but after the 9th it tails off quickly into small, weak surf. The overall pattern is a slow start, a good run in the first week of September, and then a fade.
So, for the best waves, pencil in the morning of Sunday the 6th of September. That’s your window.
Rusty.
Short Range ForecastModerate rain (total 18mm), heaviest on Thu afternoon. Warm (max 29°C on Tue morning, min 23°C on Thu afternoon). Winds decreasing (fresh winds from the SW on Wed night, calm by Thu night). | Days 4-6 Weather SummarySome drizzle, heaviest during Sun afternoon. Warm (max 27°C on Fri afternoon, min 24°C on Fri night). Wind will be generally light. | ||||||||||||||||||||
Tuesday 25 | Wednesday 26 | Thursday 27 | Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | |||||||||||||||
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) | SSE 13 | SSE 12 | S 12 | SSE 10 | SSE 9 | SSE 9 | SW 6 | E 13 | E 13 | SW 6 | E 12 | SW 6 | E 12 | E 11 | E 11 | E 12 | E 12 | E 12 | E 11 | E 11 | SE 12 |
Wave Graph  | |||||||||||||||||||||
 kJ | 1025 | 658 | 287 | 159 | 146 | 115 | 123 | 173 | 163 | 200 | 103 | 122 | 96 | 63 | 58 | 100 | 100 | 95 | 87 | 89 | 147 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | cross-on | cross-on | cross-on | cross-on | cross-on | cross-off | cross-on | off | cross-on | cross | cross-off | cross-off | cross-off | off | glassy | cross-on | cross-on | cross-on | cross-on |
High Tide | 4:27PM1.25m | 2:31AM1.30m | 4:41PM1.29m | 3:17AM1.37m | 4:57PM1.33m | 3:58AM1.42m | 5:14PM1.37m | 4:38AM1.44m | 5:32PM1.40m | 5:17AM1.43m | 5:51PM1.42m | 5:58AM1.39m | 6:10PM1.43m | ||||||||
Low Tide | 9:08AM0.28m | 9:22PM0.95m | 9:42AM0.22m | 9:51PM0.85m | 10:12AM0.19m | 10:21PM0.74m | 10:41AM0.20m | 10:51PM0.63m | 11:09AM0.24m | 11:22PM0.53m | 11:35AM0.32m | 11:54PM0.43m | 12:02PM0.43m | 00:30AM0.36m | |||||||
 | |  | | |  |  | |  |  |  |  | | | | | | | | | | |
 | 5:05 | — | — | 5:05 | — | — | 5:05 | — | — | 5:07 | — | — | 5:07 | — | — | 5:07 | — | — | 5:09 | — | — |
 | — | 6:15 | — | — | 6:14 | — | — | 6:13 | — | — | 6:12 | — | — | 6:09 | — | — | 6:08 | — | — | 6:07 | — |
mm | — | — | — | — | — | 1 | 6 | 4 | 7 | — | — | — | — | — | — | — | 1 | — | — | — | — |
Temp °C | 29 | 29 | 27 | 29 | 29 | 27 | 28 | 24 | 25 | 26 | 27 | 25 | 27 | 27 | 25 | 27 | 27 | 26 | 29 | 29 | 27 |
Feels °C | 29 | 29 | 28 | 32 | 30 | 28 | 30 | 26 | 27 | 30 | 28 | 27 | 29 | 27 | 26 | 31 | 32 | 30 | 31 | 31 | 30 |
Swell 1 Height (m) Direction Period (s) | SSE 13 | SSE 12 | SSE 10 | SSE 10 | SSE 9 | SSE 9 | SSW 6 | SSW 6 | S 9 | SSW 6 | E 12 | SSW 6 | E 12 | E 11 | E 11 | ENE 5 | E 12 | NE 6 | E 11 | ENE 7 | SE 12 |
| kJ | 1025 | 658 | 198 | 159 | 146 | 115 | 55 | 40 | 134 | 71 | 103 | 47 | 96 | 63 | 58 | 19 | 100 | 28 | 87 | 36 | 147 |
Swell 2 Height (m) Direction Period (s) | ESE 14 | ESE 13 | S 12 | SW 6 | ESE 12 | E 12 | SSE 10 | E 13 | E 13 | E 12 | S 8 | E 12 | S 8 | S 8 | SSW 8 | E 12 | SSW 8 | E 12 | SE 9 | E 11 | E 11 |
| kJ | 201 | 181 | 287 | 32 | 113 | 70 | 96 | 173 | 163 | 151 | 21 | 99 | 28 | 30 | 21 | 100 | 19 | 95 | 23 | 89 | 89 |
Swell 3 Height (m) Direction Period (s) | E 11 | — | ESE 13 | S 12 | S 12 | SSW 11 | E 11 | SSE 10 | SE 10 | S 9 | SE 9 | S 8 | SW 6 | SE 11 | SE 10 | SSW 8 | SE 10 | SSW 8 | SSW 8 | ESE 13 | S 10 |
| kJ | 84 | — | 176 | 101 | 101 | 47 | 58 | 80 | 26 | 37 | 22 | 20 | 9 | 30 | 27 | 19 | 26 | 19 | 13 | 68 | 49 |
Wind waves Height (m) Direction Period (s) | SSW 4 | SSW 5 | SSW 5 | SW 6 | SSW 5 | SSW 6 | SW 6 | SW 6 | SSW 6 | SW 6 | SW 6 | SW 6 | NE 3 | NE 4 | NE 4 | — | ENE 6 | — | NE 7 | — | — |
| kJ | 18 | 37 | 44 | 72 | 44 | 80 | 123 | 108 | 40 | 200 | 52 | 122 | 3 | 27 | 16 | — | 20 | — | 43 | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 88 | 557 | 86 | 9 | 598 | 101 | 15 | 0 | 45 | 0 | 18 | 2 | 206 | 103 | 0 | 0 | 0 | 9 | 2 | 143 | 18 |
Best forecast wave conditions in Chiba | |||||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||||
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Information about the Onjuku Surf forecast
The above surf forecast table for Onjuku provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Onjuku can be found by selecting the local surf guide option on the grey menu. Our Onjuku 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 (Onjuku) 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 Onjuku 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.
Onjuku is 3 km (2 miles) from Ohara. If you plan a holiday in Chiba, look for hotels and other accommodation in Ohara. Ohara has rooms for a wide range of budgets as well as car hire and transport links.
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