Surf Forecasts:
Onjuku surf forecast from 16 Aug 2026:
- Best quality surf: Tuesday 18 Aug, 6AM (local time) - 3ft (0.9m), 8s period, ESE swell with cross-offshore winds.
- Most powerful swell: Sunday 23 Aug, 3PM (local time) - 3ft (0.9m), 14s period, SE swell with 293 kJ wave energy.
- Next surfable swell (1★+): Tuesday 18 Aug, 6AM (local time) - 3ft (0.9m), 8s 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 Tuesday (Aug 18) at 6AM. The primary swell is predicted to be 0.9m and 8s period with a secondary swell of 0.4m 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 0.9m 14s and forecast to arrive on Sunday (Aug 23) 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 0.4m 3s period and expected on Wednesday (Aug 19) at 12PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6AM (Tue 18th Aug) | 3ft (0.9m) 8s |
| Best Surf | 6AM (Tue 18th Aug) | 3ft (0.9m) 8s |
| Most Powerful | 3PM (Sun 23rd Aug) | 3ft (0.9m) 14s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
G’day, Rusty here. Let’s talk about what’s brewing at Onjuku over the next 16 days. The start is a total drought for decent surf, so don’t rush.
The first week, from Sunday the 16th through the 23rd, is mostly a washout. Winds are cross or onshore most of the time, swell is small and weak, with combined energy mostly under 300 (moderate). Tuesday morning the 18th is the only clean window—light cross-off breeze, but the swell is a measly 3 ft from the east with a short 8-second period. Not worth the wax. Wednesday the 19th morning is also clean but tiny. The rest of that week is choppy, lumpy, or blown out, with onshore winds ruining any chance.
The real action starts Monday the 24th of August. Onjuku gets a solid groundswell—7 ft from the SSE with a very long 16-second period. Combined energy is over 2000 (strong). The wind is a clean cross-off from the NE at 12 mph, so it’ll look good. This is expert-level stuff—over 7 ft and powerful, with long period making it punchy at a beach break. Crowds are sometimes there, so you’ll have company. Water temp is 80°F, about average, so no surprises.
Another big moment is the 30th and 31st of August. Onjuku sees a huge 13 ft swell from the SE with periods around 12 to 13 seconds. Combined energy is massive—over 5000 (very strong). Winds are offshore or cross-off and clean. But this is way too big for this break—it’s for experts only. The file itself says the swell is too big for the spot.
For kite surfers, the strong onshore, lumpy days from the 22nd to the 23rd might be more fun than a paddle surfer’s day out.
So, to sum it up: the first week is a bust. Your best chance for clean, powerful waves is Monday the 24th, if you’ve got the skills. The end of August has huge swell but it’s only for the brave. Stay tuned.
Rusty.
Short Range ForecastLight rain (total 5mm), mostly falling on Sun morning. Warm (max 27°C on Tue morning, min 24°C on Sun night). Wind will be generally light. | Days 4-6 Weather SummaryMostly dry. Warm (max 27°C on Wed morning, min 25°C on Wed night). Wind will be generally light. | ||||||||||||||||||||
Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | |||||||||||||||
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 9 | E 8 | E 9 | E 9 | E 9 | ESE 8 | E 8 | E 8 | SE 7 | SE 7 | ESE 7 | ESE 7 | E 8 | E 8 | ESE 8 | ESE 7 | S 9 | ESE 9 | E 9 | ESE 10 | E 10 |
Wave Graph  | |||||||||||||||||||||
 kJ | 293 | 200 | 230 | 154 | 151 | 115 | 86 | 64 | 56 | 51 | 58 | 49 | 120 | 124 | 105 | 71 | 60 | 146 | 133 | 205 | 200 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross | cross | cross | cross | cross | cross | cross-off | cross | cross | cross-off | cross | cross-on | cross | cross-on | on | on | on | on | cross-on | cross-on | cross-on |
High Tide | 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 | 9:35PM1.21m | ||||||||||
Low Tide | 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 | 6:00AM0.49m | ||||||||||
 |  |  |  | | |  | |  | | |  | | | | | | | | | | |
 | 4:58 | — | — | 4:58 | — | — | 4:58 | — | — | 5:00 | — | — | 5:01 | — | — | 5:01 | — | — | 5:01 | — | — |
 | — | 6:27 | — | — | 6:25 | — | — | 6:23 | — | — | 6:22 | — | — | 6:22 | — | — | 6:21 | — | — | 6:19 | — |
mm | 2 | — | 1 | — | — | 2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 26 | 26 | 25 | 26 | 26 | 25 | 27 | 27 | 25 | 27 | 27 | 25 | 27 | 27 | 26 | 27 | 27 | 26 | 28 | 27 | 26 |
Feels °C | 27 | 26 | 27 | 27 | 28 | 28 | 29 | 29 | 28 | 29 | 29 | 28 | 30 | 29 | 29 | 30 | 28 | 27 | 28 | 27 | 26 |
Swell 1 Height (m) Direction Period (s) | E 9 | E 8 | E 9 | E 9 | E 9 | ESE 8 | E 8 | SE 7 | SE 7 | SE 7 | E 9 | ESE 7 | E 8 | E 8 | ESE 8 | ESE 7 | E 8 | ESE 9 | E 9 | ESE 10 | E 10 |
| kJ | 293 | 200 | 230 | 154 | 151 | 115 | 86 | 48 | 55 | 46 | 40 | 44 | 120 | 124 | 105 | 71 | 41 | 146 | 133 | 205 | 200 |
Swell 2 Height (m) Direction Period (s) | SSW 9 | S 9 | S 8 | SSW 8 | SSW 8 | SE 10 | SE 7 | E 8 | E 9 | E 8 | SE 10 | E 8 | SE 11 | SE 11 | S 9 | S 8 | S 9 | SSW 11 | S 10 | SSW 10 | SSE 10 |
| kJ | 27 | 36 | 35 | 24 | 23 | 39 | 23 | 64 | 56 | 51 | 35 | 49 | 40 | 40 | 40 | 37 | 60 | 121 | 74 | 56 | 10 |
Swell 3 Height (m) Direction Period (s) | ESE 9 | ESE 9 | SE 11 | SE 11 | SE 11 | SSW 8 | SE 10 | SE 10 | SE 10 | SE 10 | SSW 8 | SE 10 | SSE 6 | S 10 | SE 11 | SE 11 | SE 11 | SE 10 | SE 10 | SSE 11 | SE 12 |
| kJ | 32 | 35 | 31 | 30 | 30 | 13 | 36 | 27 | 36 | 35 | 6 | 35 | 3 | 17 | 42 | 56 | 41 | 37 | 25 | 12 | 6 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | NE 3 | ESE 7 | — | — | — | — | — | S 3 | — | SSW 3 | SSW 4 | SSW 5 |
| kJ | — | — | — | — | — | — | — | — | — | 1 | 58 | — | — | — | — | — | 1 | — | 3 | 21 | 54 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 73 | 9 | 103 | 57 | 9 | 0 | 9 | 9 | 0 | 56 | 9 | 56 | 9 | 9 | 9 | 9 | 9 | 205 | 583 | 557 |
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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