Surf Forecasts:
Onjuku surf forecast from 24 Aug 2026:
- Best quality surf: Tuesday 1 Sep, 9AM (local time) - 3.5ft (1.0m), 12s period, SSE swell with offshore winds.
- Most powerful swell: Tuesday 25 Aug, 9AM (local time) - 6ft (1.8m), 13s period, SSE swell with 1,025 kJ wave energy.
- Next surfable swell (1★+): Thursday 27 Aug, 6PM (local time) - 2.5ft (0.7m), 13s 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 Thursday (Aug 27) at 6PM. The primary swell is predicted to be 0.7m and 13s 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 1.8m 13s and forecast to arrive on Tuesday (Aug 25) at 9AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.9m 4s period and expected on Saturday (Aug 29) at 12PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Thu 27th Aug) | 2.5ft (0.7m) 13s |
| Best Surf | 9AM (Tue 1st Sep) | 3.5ft (1.0m) 12s |
| Most Powerful | 9AM (Tue 25th Aug) | 6ft (1.8m) 13s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let’s talk about what’s cooking at Onjuku over the next couple of weeks. It’s a bit of a mixed bag, with some real standouts on the horizon if you’re patient.
The water temp is sitting at 82°F, which is a touch warmer than normal for this time of year, so you might not need the thickest wetsuit.
We’ve got a long wait ahead. The first week is pretty grim, with the exception of one decent window. Tuesday the 25th kicks off with a 6ft SSE swell, but it’s got a nasty 25-30 km/h cross-onshore wind, making a choppy mess. The combined swell energy is strong at 1331, but the wind ruins it. Wednesday is much the same with cross-shore and onshore winds, and tiny, messy 3-3ft waves. Thursday gets a bit smaller with a 4ft SW windswell, but those thunderstorms and cross-onshore winds keep things ordinary. The only half-decent chance in the first week is Friday morning, the 28th. We get a brief window with a 5ft SW swell (period a short 6 seconds) and a light offshore NNW wind at 5 km/h. The combined energy is moderate (461) and conditions clean, but it’s a short-lived moment of goodness. The rest of the weekend into early next week is tiny, with 2ft waves and onshore to cross-offshore winds. It's just not doing anything.
Now, Tuesday the 1st of September is where it gets interesting. Tuesday morning is a standout with a solid 3ft SSE groundswell (period 12 seconds) and a gentle offshore NNE breeze (15 km/h). The combined swell energy is moderate (504) and conditions are clean. This is a good, clean, long-period swell that will hold up nicely at an exposed spot. Tuesday afternoon looks even better, with the swell building to 5ft from the SSE, light ENE cross-offshore wind at just 10 km/h, and combined energy climbing to a strong 672. The wave comment says “expect very good surf conditions.” That’s the best window in the whole forecast.
But don’t get too comfortable. Wednesday the 2nd sees a dramatic change. We’re looking at a 10ft to 12ft SSE swell with a moderate cross-onshore wind. The combined energy jumps to 1661 and then a massive 4458. This swell is way too big for most, pushing well into expert territory. For anyone but the most seasoned, this is a pass.
After that, the forecast gets wild. On Thursday the 3rd, a huge 18-20ft SSE/S swell hits with direct onshore winds. The combined energy readings are off the charts (6631 and 18957). This is massive, dangerous, and blown out. It’s not a surf day; it’s a survival day. By Friday the 4th, the swell drops back to 5-6ft but the onshore wind is still howling at 25-30 km/h, making for poor conditions. The rest of the second week is a write-off: small swells, lumpy cross-shore winds and rain. Not worth the paddle.
So, the clear highlight: Tuesday the 1st of September. Clean, long-period swell with light offshore winds. If you can wait, that’s the one to circle. The Friday the 28th of August morning is a consolation prize, but it’s short and small.
Rusty
Short Range ForecastModerate rain (total 18mm), heaviest on Thu night. Warm (max 30°C on Wed morning, min 23°C on Thu night). Winds decreasing (fresh winds from the SW on Wed night, calm by Thu night). | Days 4-6 Weather SummaryModerate rain (total 10mm), heaviest on Fri morning. Warm (max 27°C on Fri afternoon, min 23°C on Sat night). Wind will be generally light. | ||||||||||||||||||||
Tuesday 25 | Wednesday 26 | Thursday 27 | Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | |||||||||||||||
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) | SSE 13 | SSE 12 | S 12 | SSE 10 | SSE 9 | SSW 6 | SW 6 | E 13 | E 13 | SW 6 | E 12 | E 12 | E 12 | E 11 | E 11 | E 11 | E 12 | E 12 | E 11 | E 11 | SE 12 |
Wave Graph | |||||||||||||||||||||
1025 | 658 | 287 | 193 | 146 | 123 | 115 | 173 | 163 | 177 | 103 | 99 | 67 | 60 | 58 | 58 | 69 | 66 | 59 | 58 | 72 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | cross-on | cross | cross-on | cross-on | cross-on | cross | glassy | off | cross-on | cross | cross-off | cross-off | cross-off | off | cross-off | cross-off | cross-off | cross-off | cross-off |
High Tide | 4:27PM1.25m | 2:31AM1.30m | 4:41PM1.29m | 3:17AM1.37m | 4:57PM1.33m | 3:58AM1.42m | 5:14PM1.37m | 4:38AM1.44m | 5:32PM1.40m | 5:17AM1.43m | 5:51PM1.42m | 5:58AM1.39m | 6:10PM1.43m | ||||||||
Low Tide | 9:08AM0.28m | 9:22PM0.95m | 9:42AM0.22m | 9:51PM0.85m | 10:12AM0.19m | 10:21PM0.74m | 10:41AM0.20m | 10:51PM0.63m | 11:09AM0.24m | 11:22PM0.53m | 11:35AM0.32m | 11:54PM0.43m | 12:02PM0.43m | 00:30AM0.36m | |||||||
5:05 | — | — | 5:05 | — | — | 5:05 | — | — | 5:07 | — | — | 5:07 | — | — | 5:07 | — | — | 5:09 | — | — | |
— | 6:15 | — | — | 6:14 | — | — | 6:13 | — | — | 6:12 | — | — | 6:09 | — | — | 6:08 | — | — | 6:07 | — | |
mm | — | — | — | — | — | 1 | 3 | 5 | 9 | 3 | — | — | 1 | 4 | 2 | — | — | — | — | — | 1 |
Temp °C | 28 | 28 | 27 | 30 | 29 | 27 | 30 | 28 | 25 | 26 | 27 | 26 | 27 | 27 | 25 | 26 | 25 | 24 | 25 | 25 | 24 |
Feels °C | 29 | 28 | 28 | 31 | 29 | 27 | 31 | 32 | 28 | 30 | 30 | 29 | 29 | 30 | 29 | 28 | 26 | 25 | 26 | 26 | 25 |
Swell 1 Height (m) Direction Period (s) | SSE 13 | SSE 12 | SSE 10 | SSE 10 | SSE 9 | SSE 9 | SSW 6 | SSW 6 | S 9 | SSW 7 | E 12 | SSW 7 | S 7 | E 11 | E 11 | E 11 | E 12 | E 12 | E 11 | E 11 | ESE 6 |
1025 | 658 | 202 | 193 | 146 | 115 | 52 | 37 | 137 | 111 | 103 | 65 | 40 | 60 | 58 | 58 | 69 | 66 | 59 | 58 | 59 | |
Swell 2 Height (m) Direction Period (s) | ESE 14 | ESE 13 | S 12 | SW 6 | ESE 12 | E 12 | SSE 10 | E 13 | E 13 | E 12 | SE 9 | E 12 | E 12 | S 8 | SE 10 | SE 10 | SE 10 | SE 10 | NE 7 | NE 7 | E 11 |
201 | 181 | 287 | 32 | 113 | 70 | 96 | 173 | 163 | 151 | 22 | 99 | 67 | 29 | 27 | 25 | 25 | 25 | 27 | 26 | 60 | |
Swell 3 Height (m) Direction Period (s) | E 11 | — | ESE 13 | S 12 | S 12 | SSW 11 | E 11 | SSE 10 | ENE 4 | SE 9 | SE 15 | SE 9 | SE 11 | SE 11 | SSW 8 | SSW 8 | SSW 8 | NE 8 | SE 9 | SE 9 | SE 12 |
84 | — | 176 | 101 | 101 | 48 | 58 | 80 | 5 | 22 | 8 | 23 | 30 | 30 | 21 | 11 | 11 | 10 | 22 | 22 | 72 | |
Wind waves Height (m) Direction Period (s) | SW 4 | SSW 5 | SW 5 | SW 6 | SW 5 | SSW 6 | SW 6 | — | SW 6 | SW 6 | SSW 6 | — | ENE 4 | ENE 5 | E 5 | E 5 | E 5 | ESE 5 | ESE 5 | ESE 6 | S 3 |
21 | 37 | 51 | 72 | 57 | 123 | 115 | — | 77 | 177 | 94 | — | 13 | 39 | 28 | 22 | 22 | 35 | 42 | 43 | 6 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 88 | 240 | 18 | 9 | 598 | 18 | 17 | 2 | 0 | 0 | 17 | 2 | 2 | 0 | 0 | 0 | 57 | 16 | 16 | 56 | 16 |
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.











