
Surf Forecasts:
Onjuku surf forecast from 12 Aug 2026:
- Best quality surf: Monday 17 Aug, 12AM (local time) - 8ft (2.5m), 11s period, E swell with cross-offshore winds.
- Most powerful swell: Sunday 16 Aug, 3PM (local time) - 8ft (2.5m), 10s period, E swell with 1,506 kJ wave energy.
- Next surfable swell (1★+): Wednesday 12 Aug, 6PM (local time) - 4ft (1.2m), 9s 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 Wednesday (Aug 12) at 6PM. The primary swell is predicted to be 1.2m and 9s period with a secondary swell of 0.5m and 10s. Another secondary swell of 0.7m and 5s 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 2.5m 10s and forecast to arrive on Sunday (Aug 16) at 3PM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Friday (Aug 14) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Wed 12th Aug) | 4ft (1.2m) 9s |
| Best Surf | 12AM (Mon 17th Aug) | 8ft (2.5m) 11s |
| Most Powerful | 3PM (Sun 16th Aug) | 8ft (2.5m) 10s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright, Rusty here. Let's have a look at what’s cooking for Onjuku.
Right now, the outlook starts with a bit of a wait. The first surf worth paddling out for won't really show up until Thursday the 13th. The water temp is sitting at a warm 82°F, which is about a degree and a half warmer than usual for this time of year, so you can get away with just a spring suit.
On Wednesday the 12th, it's a write-off. We’ve got messy conditions with a risk of thunderstorms, cross-onshore winds, and 7ft of average ESE swell with only a 9-second period and weak energy (762). Thursday the 13th is when things start to clean up. The morning shows 5ft of E swell at 9 seconds with moderate energy (454) and a nice cross-offshore breeze. It's not pumping, but it's clean and surfable. The afternoon stays similar at 5ft with a slightly longer 10-second period (480). Both sessions get a thumbs-up for *good surf conditions*.
Friday the 14th stays in that same groove with 5ft swell and cross-off winds, but the energy ticks up a notch (501) and the strength is there. The mornings look better than the afternoons, both are marginal but clean.
Saturday the 15th gets a little tricky. We see the swell bump up to 6ft from the east, but the wind swings cross-shore, putting a chop on the surface. The afternoon cleans up again with cross-offshore wind and 6ft (554 energy). Still, nothing that will blow your mind.
Now we get to the first standout. Sunday the 16th. The swell picks up to 8ft in the morning and 8ft in the afternoon, from the ESE and E respectively, with a 10-second period. This is where the energy really fires up – we’re talking 1069 in the morning and a massive 2696 in the afternoon. That's strong, powerful surf. The wind is offshore from the NE at 16 mph keeping it clean. This is expert territory at 8ft, but for those who can handle it, Sunday afternoon is the best on offer in this whole run. The break at Onjuku is exposed to the SSE, and we’re getting ESE to E swell, so it’s a good match.
Monday the 17th holds decent size at 7ft and 7ft, but with moderate offshore winds (12 mph in the morning, lighter 9 mph in the afternoon). The afternoon session gets an *expect very good surf conditions* call, with 797 energy. The swell direction swings a little more ENE, which is a bit off the optimum SSE, but still workable.
Tuesday the 18th drops off significantly to 4ft with an 8-second period. It’ll be small and weak (237 energy). Wednesday the 19th through Friday the 21st is a flat spell with tiny, weak swell and onshore crud. Not worth the drive.
Then, a wildcard on Saturday the 22nd. The morning shows 6ft of NE windswell with a 7-second period and a strong 25 mph offshore wind. That wind is so strong it's hard to paddle into, but the afternoon calms down to 6 mph offshore with 6ft and 413 energy. This is a fickle one for the experts – a short-period, messy windswell, but clean in the afternoon.
From Sunday the 23rd right through to the end on the 27th, it's mostly small, weak, and onshore, with the exception of a glassy morning on Thursday the 27th with 6ft ENE swell at 7 seconds (good energy at 391). It’s a blink-and-you’ll-miss-it window.
So, to sum it up: the absolute standouts are Sunday the 16th afternoon for the big, clean power (8ft, 2696 energy, offshore wind), and Monday the 17th afternoon for very good conditions with still solid size. Everything else is either small, marginal, or for the hardcore only.
Stay safe.
Rusty.
Short Range ForecastHeavy rain (total 42mm), heaviest during Wed morning. Warm (max 27°C on Thu morning, min 23°C on Wed night). Wind will be generally light. | Days 4-6 Weather SummarySome drizzle, heaviest during Sat morning. Warm (max 27°C on Sat morning, min 23°C on Sun night). Wind will be generally light. | ||||||||||||||||||||
Wednesday 12 | Thursday 13 | Friday 14 | Saturday 15 | Sunday 16 | Monday 17 | Tuesday 18 | |||||||||||||||
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) | ESE 9 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 9 | E 9 | E 9 | ESE 10 | E 10 | E 11 | E 10 | ENE 9 | ENE 9 | ENE 8 | ENE 8 | SSE 10 |
Wave Graph | |||||||||||||||||||||
669 | 201 | 318 | 383 | 426 | 434 | 443 | 434 | 414 | 484 | 495 | 734 | 1018 | 1506 | 1379 | 919 | 739 | 322 | 185 | 119 | 178 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-off | off | cross-off | cross-off | cross-off | cross-off | cross-off | cross | cross | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | on | cross-on |
High Tide | 5:21PM1.37m | 3:50AM1.49m | 5:43PM1.38m | 4:40AM1.50m | 6:04PM1.38m | 5:27AM1.47m | 6:24PM1.39m | 6:12AM1.40m | 6:43PM1.39m | 6:57AM1.29m | 7:02PM1.40m | 7:43AM1.18m | 7:22PM1.39m | ||||||||
Low Tide | 10:15AM0.00m | 10:23PM0.88m | 10:54AM0.03m | 11:01PM0.75m | 11:29AM0.11m | 11:38PM0.63m | 12:00PM0.24m | 00:15AM0.53m | 12:27PM0.38m | 00:54AM0.46m | 12:51PM0.53m | 1:34AM0.43m | 1:11PM0.67m | 2:17AM0.43m | |||||||
4:54 | — | — | 4:56 | — | — | 4:56 | — | — | 4:56 | — | — | 4:58 | — | — | 4:58 | — | — | 4:58 | — | — | |
— | 6:30 | — | — | 6:30 | — | — | 6:29 | — | — | 6:28 | — | — | 6:27 | — | — | 6:25 | — | — | 6:23 | — | |
mm | 10 | 7 | 1 | 2 | — | 4 | 1 | — | 17 | 1 | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 26 | 26 | 24 | 27 | 27 | 25 | 27 | 27 | 25 | 27 | 27 | 25 | 26 | 26 | 24 | 25 | 25 | 24 | 25 | 26 | 25 |
Feels °C | 26 | 28 | 27 | 29 | 29 | 28 | 28 | 28 | 28 | 27 | 27 | 26 | 25 | 25 | 25 | 25 | 25 | 26 | 27 | 28 | 27 |
Swell 1 Height (m) Direction Period (s) | S 6 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 9 | E 9 | E 9 | ESE 10 | E 10 | E 11 | E 10 | SSW 9 | ENE 9 | ENE 8 | ENE 8 | SSE 10 |
34 | 201 | 318 | 383 | 426 | 434 | 443 | 434 | 414 | 484 | 495 | 476 | 1018 | 1160 | 1379 | 919 | 29 | 322 | 185 | 119 | 178 | |
Swell 2 Height (m) Direction Period (s) | S 10 | S 10 | S 10 | S 10 | S 10 | SSW 9 | SSW 9 | S 9 | S 10 | S 11 | S 10 | S 9 | S 9 | S 10 | S 9 | SSW 10 | SE 11 | SSW 8 | SSW 9 | SSE 10 | E 9 |
53 | 53 | 51 | 71 | 48 | 29 | 28 | 40 | 67 | 63 | 53 | 41 | 27 | 30 | 25 | 31 | 19 | 24 | 25 | 68 | 38 | |
Swell 3 Height (m) Direction Period (s) | SE 13 | S 6 | S 5 | — | SE 12 | SSE 11 | SE 11 | SSE 11 | S 13 | SSE 10 | SSE 8 | SE 12 | SSW 11 | — | — | SE 16 | SE 16 | SE 10 | SE 10 | S 15 | NE 8 |
6 | 16 | 8 | — | 6 | 12 | 30 | 23 | 50 | 31 | 6 | 6 | 24 | — | — | 10 | 10 | 28 | 27 | 4 | 20 | |
Wind waves Height (m) Direction Period (s) | ESE 9 | E 5 | — | — | — | — | — | — | — | — | — | E 9 | — | E 10 | — | — | ENE 9 | — | — | SW 4 | SW 4 |
669 | 53 | — | — | — | — | — | — | — | — | — | 734 | — | 1506 | — | — | 739 | — | — | 15 | 18 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 91 | 68 | 0 | 0 | 0 | 0 | 51 | 51 | 9 | 68 | 68 | 22 | 51 | 51 | 0 | 51 | 0 | 0 | 0 | 9 | 9 |
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.











