Surf Forecasts:
Onjuku surf forecast from 15 Aug 2026:
- Best quality surf: Sunday 16 Aug, 6AM (local time) - 4.5ft (1.4m), 10s period, E swell with cross-offshore winds.
- Most powerful swell: Saturday 15 Aug, 9PM (local time) - 5ft (1.5m), 10s period, ESE swell with 391 kJ wave energy.
- Next surfable swell (1★+): Saturday 15 Aug, 9PM (local time) - 5ft (1.5m), 10s 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 Saturday (Aug 15) at 9PM. The primary swell is predicted to be 1.5m and 10s period with a secondary swell of 0.5m 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 1.5m 10s and forecast to arrive on Saturday (Aug 15) at 9PM. 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 Wednesday (Aug 19) at 12PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Sat 15th Aug) | 5ft (1.5m) 10s |
| Best Surf | 6AM (Sun 16th Aug) | 4.5ft (1.4m) 10s |
| Most Powerful | 9PM (Sat 15th Aug) | 5ft (1.5m) 10s |
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 on the table for the next couple of weeks at Onjuku.
Honestly, the next week or so is a grind. We’ve got some small, weak energy bumping around, but the wind is mostly cross or onshore, so the quality is just not there. The water temp is about 80°, which is bang on average for this time of year, so at least you won’t be freezing while you’re sitting there waiting.
It’s not until the end of next week that things start to get interesting. There’s a solid run of south-southeast groundswell building from Monday the 24th of August, with the combined energy jumping way up into the thousands (1313 on Monday morning, then ramping to 4472 by the afternoon). That’s a serious amount of energy in the water. But here’s the catch – it’s all onshore wind. The period is long, hitting 17 to 18 seconds, which is proper groundswell, and a swell over 8 feet like the Monday afternoon reading of 8 ft is expert territory only, especially with the onshore chop. The break is exposed to the SSE, but with strong south winds, the surface will be messy.
Now, the real standout is Wednesday the 26th of August. The morning session there is the pick of the whole outlook. We’re looking at a solid 12 ft swell from the SE, with a period of 13 seconds. That’s big, powerful groundswell. The wind is cross-offshore from the east at 9 mph. The combined energy is a massive 4382. That’s a lot of grunt. The catch here is that the file calls it “too big for this break” – 12 ft is going to be a washing machine, proper heavy and likely closing out for most. This is strictly for expert-level surfers only. If you’re not on your game, sit this one out. But for the crew that can handle it, with that offshore wind, it might be a wild, memorable session. On Wednesday afternoon, it drops back to 8 ft from the ESE, still clean with cross-offshore wind, making for a much more manageable, still powerful option for strong intermediates and above.
After that, the swell fades fast through the end of the month, with the wind going back onshore or becoming too strong, so don’t sleep on that Wednesday morning window. It’s a long way out, so keep an eye on the forecasts, but that’s the one to circle on the calendar.
Rusty.
Short Range ForecastLight rain (total 4mm), mostly falling on Sat night. Warm (max 27°C on Sun morning, min 23°C on Sat night). Wind will be generally light. | Days 5-7 Weather SummaryMostly dry. Warm (max 27°C on Tue afternoon, min 24°C on Tue night). Wind will be generally light. | |||||||||||||||||||
Sat 15 | Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | ||||||||||||||
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 10 | ESE 9 | E 9 | E 8 | E 9 | E 9 | E 8 | ESE 8 | E 8 | SE 8 | SE 7 | ESE 7 | E 7 | E 7 | E 7 | E 8 | ESE 7 | ESE 7 | ESE 7 | ESE 8 |
Wave Graph | ||||||||||||||||||||
391 | 308 | 256 | 200 | 230 | 181 | 144 | 115 | 86 | 69 | 73 | 84 | 74 | 106 | 88 | 118 | 125 | 99 | 108 | 93 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross | cross-off | cross | cross | cross | cross | cross | cross | cross-off | cross | cross | cross-off | cross | cross-on | cross | cross-on | cross-on | glassy | cross-on | glassy |
High Tide | 6:24PM1.39m | 6:12AM1.40m | 6:43PM1.39m | 6:57AM1.29m | 7:02PM1.40m | 7:43AM1.18m | 7:22PM1.39m | 8:37AM1.06m | 7:42PM1.36m | 9:58AM0.96m | 8:05PM1.32m | 8:35PM1.27m | ||||||||
Low Tide | 00:15AM0.53m | 12:27PM0.38m | 00:54AM0.46m | 12:51PM0.53m | 1:34AM0.43m | 1:11PM0.67m | 2:17AM0.43m | 1:24PM0.80m | 3:09AM0.46m | 1:21PM0.89m | 4:20AM0.49m | |||||||||
— | — | 4:58 | — | — | 4:58 | — | — | 4:58 | — | — | 5:00 | — | — | 5:01 | — | — | 5:01 | — | — | |
6:28 | — | — | 6:27 | — | — | 6:25 | — | — | 6:23 | — | — | 6:22 | — | — | 6:22 | — | — | 6:21 | — | |
mm | — | 1 | 1 | — | 2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 26 | 24 | 27 | 26 | 24 | 26 | 26 | 25 | 27 | 27 | 25 | 27 | 27 | 25 | 27 | 26 | 25 | 27 | 27 | 26 |
Feels °C | 26 | 25 | 28 | 26 | 25 | 27 | 28 | 28 | 29 | 29 | 28 | 29 | 29 | 28 | 30 | 28 | 27 | 30 | 29 | 29 |
Swell 1 Height (m) Direction Period (s) | ESE 10 | ESE 9 | E 9 | S 8 | E 9 | E 9 | E 8 | ESE 8 | E 8 | SE 8 | SE 7 | ESE 7 | E 9 | E 7 | E 7 | E 8 | ESE 7 | ESE 7 | SE 10 | ESE 8 |
391 | 308 | 256 | 35 | 230 | 181 | 144 | 115 | 86 | 69 | 73 | 84 | 23 | 106 | 88 | 118 | 125 | 99 | 37 | 93 | |
Swell 2 Height (m) Direction Period (s) | S 10 | S 9 | SSW 9 | ESE 9 | S 9 | SSW 8 | SE 11 | SE 10 | SE 7 | E 8 | E 9 | E 9 | SE 10 | SE 10 | SE 11 | SE 11 | SE 11 | SE 11 | S 8 | SSW 8 |
53 | 41 | 27 | 35 | 23 | 24 | 30 | 38 | 30 | 64 | 56 | 23 | 35 | 36 | 40 | 40 | 40 | 40 | 18 | 19 | |
Swell 3 Height (m) Direction Period (s) | SSE 9 | SE 10 | ESE 9 | SE 11 | SE 11 | SE 11 | SSW 8 | SSW 8 | SE 10 | SE 10 | SE 10 | SE 10 | SSW 8 | SSE 6 | SSW 9 | SSW 9 | S 8 | S 8 | SE 15 | SE 10 |
15 | 27 | 32 | 32 | 31 | 30 | 23 | 13 | 36 | 27 | 26 | 25 | 6 | 4 | 8 | 16 | 21 | 18 | 9 | 35 | |
Wind waves Height (m) Direction Period (s) | — | — | — | E 8 | — | — | — | — | — | — | — | ENE 9 | E 7 | — | — | SSE 6 | — | — | ESE 7 | S 4 |
— | — | — | 200 | — | — | — | — | — | — | — | 65 | 74 | — | — | 3 | — | — | 108 | 7 | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 68 | 0 | 51 | 103 | 51 | 51 | 56 | 18 | 0 | 9 | 17 | 0 | 51 | 9 | 56 | 9 | 9 | 0 | 9 | 0 |
Best forecast wave conditions in Chiba | ||||||||||||||||||||
Best forecast wave conditions in Japan | ||||||||||||||||||||
Header Global | ||||||||||||||||||||
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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.











