
Surf Forecasts:
Onjuku surf forecast from 9 Aug 2026:
- Best quality surf: Monday 10 Aug, 3AM (local time) - 6ft (1.8m), 12s period, ESE swell with offshore winds.
- Most powerful swell: Saturday 15 Aug, 3PM (local time) - 10ft (3.0m), 12s period, E swell with 2,344 kJ wave energy.
- Next surfable swell (1★+): Sunday 9 Aug, 9PM (local time) - 5.5ft (1.7m), 12s period with ESE 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 Sunday (Aug 09) at 9PM. The primary swell is predicted to be 1.7m and 12s period with a secondary swell of 0.7m and 10s. 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 3.0m 12s and forecast to arrive on Saturday (Aug 15) 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 2.0m 8s period and expected on Tuesday (Aug 11) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Sun 9th Aug) | 5.5ft (1.7m) 12s |
| Best Surf | 3AM (Mon 10th Aug) | 6ft (1.8m) 12s |
| Most Powerful | 3PM (Sat 15th Aug) | 10ft (3.0m) 12s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let's have a look at what's cookin' for Onjuku over the next couple of weeks. It's a bit of a mixed bag, so we need to pick our moments.
The first real standout is going to be Tuesday morning, the 11th of August. We've got a solid 6ft of east-northeast swell rolling in with a 10-second period, and the wind is going to be a clean offshore from the north, only at 9 mph. That's going to set up some clean, well-shaped lines. The energy is strong, at 1351, and it's an exposed break, so it'll be handling that power. It's a good session for experienced surfers, as this size could be a bit much for beginners. The water temp is sitting at a comfortable 81°, which is pretty much spot on for this time of year, so no wetsuit worries.
As we move through the rest of the first week, we see a pulse of bigger swell. The morning of Friday the 14th is another one to have on your radar. You've got 6ft of east swell at 10 seconds, with a moderate offshore wind from the north. That's a clean setup, and the energy is solid at 765. Saturday the 15th sees the swell peak, hitting 8ft in the morning and even 10ft in the afternoon, but there's a risk of thunderstorms and the winds are more cross-off. That 10ft is expert territory.
Now, we hit a bit of a lull. From Sunday the 16th through to the end of the third week of August, things get pretty weak and choppy. The swell drops, and the winds swing onshore from the south and southwest, making for poor conditions. There are some clean, small waves on Monday the 17th, with only 3ft of east swell, but it’s a bit of a tease.
The real sneaky winner comes at the end of the period. Look at Sunday the 23rd of August – morning session. We get a clean, light offshore breeze from the north-northeast, and a 4ft southerly swell with a 12-second period. That long period groundswell will wrap in nicely at this exposed spot, and with clean, light winds, it'll be glassy and fun. The energy is moderate at 471, but the quality will be there. The winds will shift cross-shore by afternoon, so make the most of the morning. It's a promising call for later in the window, but we all know long-range forecasts can change.
For the rest of the time, don't bother. There are long stretches of onshore wind and messy, small surf. It’s a waiting game for those two standout windows.
Rusty.
Short Range ForecastModerate rain (total 19mm), heaviest on Wed morning. Warm (max 28°C on Sun afternoon, min 22°C on Mon night). Mainly fresh winds. | Days 5-7 Weather SummaryHeavy rain (total 36mm), heaviest during Thu night. Warm (max 28°C on Thu morning, min 24°C on Wed night). Wind will be generally light. | |||||||||||||||||||
Sun 9 | Monday 10 | Tuesday 11 | Wednesday 12 | Thursday 13 | Friday 14 | Saturday 15 | ||||||||||||||
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 13 | ESE 12 | E 12 | E 11 | ENE 10 | ENE 10 | E 11 | ENE 11 | E 10 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 11 | E 12 | E 10 |
Wave Graph | ||||||||||||||||||||
903 | 794 | 1227 | 1095 | 860 | 739 | 663 | 427 | 312 | 162 | 196 | 318 | 400 | 580 | 682 | 533 | 567 | 1201 | 2344 | 890 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross | cross-off | cross-off | cross-off | off | off | cross-off | on | cross | cross-off | cross-off | cross-off | cross-off | cross-off | off | cross-off | off | cross-off | cross-off | cross-on |
High Tide | 4:10PM1.23m | 00:23AM1.32m | 4:33PM1.30m | 1:48AM1.37m | 4:57PM1.35m | 2:54AM1.44m | 5:21PM1.37m | 3:50AM1.49m | 5:43PM1.38m | 4:40AM1.50m | 6:04PM1.38m | 5:27AM1.47m | 6:24PM1.39m | |||||||
Low Tide | 7:43PM1.16m | 8:40AM0.12m | 8:57PM1.09m | 9:31AM0.04m | 9:44PM0.99m | 10:15AM0.00m | 10:23PM0.88m | 10:54AM0.03m | 11:01PM0.75m | 11:29AM0.11m | 11:38PM0.63m | 12:00PM0.24m | 00:15AM0.53m | |||||||
— | — | 4:52 | — | — | 4:54 | — | — | 4:54 | — | — | 4:56 | — | — | 4:56 | — | — | 4:56 | — | — | |
6:35 | — | — | 6:32 | — | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — | — | 6:29 | — | — | 6:28 | — | |
mm | — | — | — | — | — | — | 2 | 9 | 8 | 3 | 5 | 1 | 1 | 13 | 2 | 6 | 1 | 4 | 1 | 2 |
Temp °C | 28 | 25 | 26 | 26 | 24 | 27 | 27 | 25 | 26 | 27 | 25 | 28 | 28 | 26 | 25 | 26 | 25 | 26 | 27 | 26 |
Feels °C | 29 | 27 | 25 | 25 | 22 | 27 | 27 | 25 | 27 | 28 | 27 | 28 | 28 | 28 | 26 | 27 | 26 | 26 | 28 | 30 |
Swell 1 Height (m) Direction Period (s) | ESE 13 | ESE 12 | E 12 | SSW 11 | S 10 | ENE 10 | E 11 | ENE 11 | E 10 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 11 | E 12 | E 10 |
903 | 794 | 1227 | 97 | 78 | 739 | 663 | 427 | 312 | 162 | 196 | 318 | 400 | 580 | 682 | 533 | 567 | 1201 | 2344 | 890 | |
Swell 2 Height (m) Direction Period (s) | S 10 | S 10 | S 11 | SW 11 | SE 14 | S 10 | NE 9 | ESE 11 | S 10 | S 10 | S 10 | S 10 | S 10 | SSW 10 | S 12 | SSE 11 | SSE 10 | S 11 | SSW 11 | S 10 |
141 | 102 | 93 | 103 | 8 | 55 | 164 | 314 | 75 | 75 | 51 | 51 | 50 | 31 | 67 | 135 | 163 | 10 | 40 | 45 | |
Swell 3 Height (m) Direction Period (s) | SW 12 | SW 12 | SW 12 | SSE 11 | SE 13 | SW 11 | S 11 | S 10 | SSW 10 | SSE 12 | — | — | SE 11 | SSE 14 | SSW 9 | SSW 9 | SSW 9 | SE 19 | SE 18 | SE 12 |
90 | 23 | 23 | 11 | 27 | 43 | 58 | 74 | 130 | 14 | — | — | 5 | 40 | 16 | 16 | 8 | 15 | 13 | 35 | |
Wind waves Height (m) Direction Period (s) | — | — | NNE 5 | E 11 | ENE 10 | NE 9 | — | S 3 | E 3 | ENE 4 | ENE 4 | — | — | — | — | — | — | — | NNE 6 | — |
— | — | 50 | 1095 | 860 | 514 | — | 5 | 6 | 17 | 12 | — | — | — | — | — | — | — | 303 | — | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 57 | 12 | 56 | 51 | 51 | 0 | 2 | 9 | 51 | 0 | 0 | 51 | 51 | 51 | 0 | 81 | 0 | 84 | 110 | 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.











