Surf Forecasts:
Onjuku surf forecast from 11 Aug 2026:
- Best quality surf: Sunday 16 Aug, 12AM (local time) - 8ft (2.4m), 10s period, E swell with offshore winds.
- Most powerful swell: Sunday 16 Aug, 12PM (local time) - 8ft (2.4m), 11s period, E swell with 1,326 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 0.8m and 5s. 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 2.4m 11s and forecast to arrive on Sunday (Aug 16) at 12PM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.5m 3s period and expected on Friday (Aug 14) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Wed 12th Aug) | 4ft (1.2m) 9s |
| Best Surf | 12AM (Sun 16th Aug) | 8ft (2.4m) 10s |
| Most Powerful | 12PM (Sun 16th Aug) | 8ft (2.4m) 11s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
G’day, Rusty here. Let’s have a yarn about the surf coming up around Onjuku over the next couple weeks. It’s a bit of a tease—there’s one real gem, but you’ll have to work through some average days to get to it.
The first few days (Tuesday 11th through Friday 14th August) are pretty average. Tuesday morning has 7ft of east swell with a 10-second period, carrying moderate wave energy (1115). The wind is cross-off from the NNW, so it’s clean enough for a paddle, but the forecast feels marginal. The water temp is a balmy 81°, which is right around average for this time of year—nothing unusual. After that, things go downhill with onshores and lumpy conditions through Wednesday and Thursday. Friday holds steady at 5ft east swell (10 seconds) and clean cross-off winds, but again, nothing special.
Then comes the standout. Sunday 16th August is your window. The morning is looking excellent for experienced surfers: a solid 8ft of east swell with a longer 11-second period, packing in strong wave energy (1332). The wind is pure offshore from the NNE at 15 mph. That’s clean, lined-up, and punchy. This is the pick of the whole forecast. The offshore wind will keep the faces glassy, and the longer period means more shape and power. It’s a proper groundswell—best on the points or reefs around here if you can find them. Be aware: at 8ft, this is for experienced crew only; beginners should sit this one out.
After Sunday, the surf drops off fast. Monday 17th is a write-off with onshore slop. Tuesday 18th has tiny 2ft swell with glassy conditions (light SSW at 3 mph) but barely enough energy (129) to push a longboard. From there, we hit a long gap. Through Wednesday 19th all the way into the following Tuesday 25th and Wednesday 26th August, there’s nothing worth paddling for. The swell stays small, the winds turn onshore or cross-onshore, and the energy readings stay low (often under 200). The only flicker is Saturday 22nd afternoon with a tiny 1ft swell but a very long 15-second period—evidence of a distant groundswell—but with clean cross-off winds, you’d be scratching for a wave.
Bottom line: this forecast is a one-hit wonder. Sunday 16th morning is the clear standout—8ft east swell, offshore winds, clean and powerful. If you’re an experienced surfer, be on it. After that, the shop is closed for the week.
Rusty.
Short Range ForecastHeavy rain (total 50mm), heaviest during Tue afternoon. Warm (max 27°C on Thu morning, min 23°C on Tue night). Winds decreasing (fresh winds from the WSW on Tue afternoon, light winds from the NNE by Wed night). | Days 4-6 Weather SummaryModerate rain (total 15mm), heaviest on Fri night. Warm (max 27°C on Fri morning, min 22°C on Sat night). Winds decreasing (fresh winds from the NE on Sat afternoon, calm by Sun night). | ||||||||||||||||||||
Tuesday 11 | Wednesday 12 | Thursday 13 | Friday 14 | Saturday 15 | Sunday 16 | Monday 17 | |||||||||||||||
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 10 | E 12 | E 11 | ESE 9 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 9 | E 9 | E 10 | E 11 | E 11 | E 10 | ENE 9 | ENE 9 | ENE 8 |
Wave Graph  | |||||||||||||||||||||
 kJ | 969 | 1215 | 514 | 586 | 239 | 274 | 383 | 494 | 434 | 441 | 441 | 408 | 695 | 606 | 1154 | 1230 | 1188 | 802 | 418 | 202 | 96 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | cross-on | on | cross | cross-off | off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | off | off | cross-off | glassy | on | on | off |
High Tide | 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 | 6:12AM1.40m | 6:43PM1.39m | 6:57AM1.29m | 7:02PM1.40m | ||||||||
Low Tide | 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 | 12:27PM0.38m | 00:54AM0.46m | 12:51PM0.53m | 1:34AM0.43m | |||||||
 |  |  |  |  |  | | | | | | | |  |  |  | | | | | | |
 | 4:54 | — | — | 4:54 | — | — | 4:56 | — | — | 4:56 | — | — | 4:56 | — | — | 4:58 | — | — | 4:58 | — | — |
 | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — | — | 6:29 | — | — | 6:28 | — | — | 6:27 | — | — | 6:25 | — |
mm | — | 14 | 18 | 5 | 6 | 2 | 1 | 1 | 3 | 1 | 1 | 10 | 3 | — | — | — | — | — | — | — | — |
Temp °C | 25 | 24 | 24 | 25 | 26 | 24 | 27 | 27 | 25 | 27 | 27 | 25 | 26 | 26 | 24 | 26 | 26 | 25 | 27 | 27 | 25 |
Feels °C | 22 | 22 | 22 | 25 | 28 | 27 | 29 | 29 | 28 | 28 | 28 | 27 | 25 | 24 | 23 | 25 | 25 | 27 | 29 | 29 | 27 |
Swell 1 Height (m) Direction Period (s) | E 10 | E 12 | E 11 | S 10 | E 9 | E 9 | E 9 | E 10 | E 10 | E 10 | E 10 | E 10 | E 9 | SSW 10 | E 10 | E 11 | E 11 | E 10 | ENE 9 | ENE 9 | ENE 8 |
| kJ | 969 | 1215 | 514 | 53 | 239 | 274 | 383 | 494 | 434 | 441 | 441 | 408 | 495 | 36 | 761 | 1230 | 1188 | 802 | 418 | 202 | 96 |
Swell 2 Height (m) Direction Period (s) | S 10 | NE 10 | S 10 | SE 13 | ESE 5 | S 6 | S 10 | S 10 | SSE 12 | SSE 11 | SSE 10 | SSE 9 | SSW 8 | SSE 8 | S 10 | S 11 | S 10 | SE 11 | S 9 | SE 11 | SE 10 |
| kJ | 55 | 707 | 53 | 6 | 36 | 26 | 71 | 48 | 59 | 68 | 54 | 44 | 14 | 7 | 47 | 61 | 50 | 41 | 25 | 40 | 27 |
Swell 3 Height (m) Direction Period (s) | SSW 11 | SE 13 | SW 10 | SSW 6 | S 10 | S 10 | — | SE 12 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSE 8 | SE 18 | SE 12 | SSW 11 | SSE 11 | SSW 9 | SE 11 | SE 16 | SSW 8 |
| kJ | 91 | 27 | 39 | 23 | 53 | 51 | — | 6 | 28 | 28 | 28 | 27 | 14 | 13 | 6 | 41 | 12 | 28 | 30 | 10 | 14 |
Wind waves Height (m) Direction Period (s) | NNE 9 | SW 11 | SSW 6 | ESE 9 | E 4 | — | — | — | — | NNE 3 | — | — | E 9 | E 9 | E 10 | — | — | — | — | SSW 8 | SSW 3 |
| kJ | 944 | 115 | 150 | 586 | 12 | — | — | — | — | 7 | — | — | 695 | 606 | 1154 | — | — | — | — | 73 | 5 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 2 | 200 | 143 | 536 | 40 | 0 | 0 | 51 | 0 | 51 | 51 | 0 | 206 | 51 | 0 | 0 | 57 | 0 | 9 | 9 | 0 |
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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