Surf Forecasts:
Onjuku surf forecast from 28 Aug 2026:
- Best quality surf: Friday 28 Aug, 9PM (local time) - 4.5ft (1.3m), 7s period, SW swell with glassy winds.
- Most powerful swell: Tuesday 1 Sep, 3PM (local time) - 3.5ft (1.0m), 12s period, ESE swell with 288 kJ wave energy.
- Next surfable swell (1★+): Friday 28 Aug, 9PM (local time) - 4.5ft (1.3m), 7s period with SW 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 Friday (Aug 28) at 9PM. The primary swell is predicted to be 1.3m and 7s period with a secondary swell of 0.6m and 7s. Another secondary swell of 0.6m and 8s is also forecast. The wind is predicted to be glassy as the swell arrives.
The most powerful waves expected at Onjuku in the next 16 days are 1.0m 12s and forecast to arrive on Tuesday (Sep 01) 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 1.1m 5s period and expected on Saturday (Aug 29) at 3PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Fri 28th Aug) | 4.5ft (1.3m) 7s |
| Best Surf | 9PM (Fri 28th Aug) | 4.5ft (1.3m) 7s |
| Most Powerful | 3PM (Tue 1st Sep) | 3.5ft (1.0m) 12s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Righto, grab a coffee, let’s see what Onjuku’s got cookin’ over the next couple of weeks. Honestly, for a spot that’s usually a goer, the start of this run is a bit of a flat, windy dud. We’ve got no real surf to speak of for the first ten days or so—just tiny, messy, blown-out scraps. The water temp is sittin’ around 82°, which is a touch warmer than normal for this time of year, so at least you won’t be cold while you’re gettin’ skunked.
We finally get a pulse toward the end of the first week of September, but it's nothin' to write home about. Sunday the 6th of September sees the energy climb a bit—combined energy hitting 672—but it’s still all cross-onshore and lumpy, so not worth paddlin’ out for.
Now, Tuesday the 8th of September is our first real glimpse of something clean. A moderate offshore breeze from the north cleans things up, with a 3ft S swell, period 10 seconds. It’s small but rideable, and with moderate offshore wind, you’ll get some fun little lines. Not a standout, but a nice change from the garbage before it.
The real standout, though, comes Thursday the 10th of September. We’ve got a proper SSE groundswell, 8ft with a long 15-second period, and the energy is massive at 2695. The wind is a clean, cross-off from the ENE. This is a big, powerful swell—definitely for experienced surfers only. That long period means it’ll be a bit straight and fast on the beachbreaks, but Onjuku can handle it. If you’re an expert, this is your window. Friday the 11th is still big and solid, though the wind starts to get a bit cross-on later in the day. Saturday the 12th is still big, but the wind turns onshore and messy, so the window is tight.
So, bottom line: don’t bother until the 8th for a little small clean-up, but your absolute target is Thursday the 10th of September for the biggest, cleanest swell of the period. After that, it fades into wind chop.
Rusty.
Short Range ForecastSome drizzle, heaviest during Fri night. Warm (max 30°C on Fri afternoon, min 23°C on Sat afternoon). Winds decreasing (fresh winds from the WSW on Fri morning, calm by Sun night). | Days 4-6 Weather SummaryLight rain (total 8mm), mostly falling on Wed morning. Warm (max 29°C on Mon morning, min 26°C on Mon night). Wind will be generally light. | ||||||||||||||||||||
Friday 28 | Saturday 29 | Sunday 30 | Monday 31 | Tuesday 1 | Wednesday 2 | Thursday 3 | |||||||||||||||
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 12 | E 12 | E 12 | E 12 | E 11 | E 11 | E 11 | E 11 | E 11 | E 11 | E 11 | ESE 12 | ESE 11 | ESE 12 | ESE 11 | ESE 11 | S 10 | SSW 10 | S 11 | S 6 | SSW 10 |
Wave Graph  | |||||||||||||||||||||
 kJ | 151 | 103 | 99 | 67 | 63 | 58 | 59 | 61 | 56 | 37 | 57 | 129 | 229 | 288 | 226 | 161 | 130 | 136 | 233 | 190 | 82 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross | cross-off | cross-off | cross-off | cross-off | off | glassy | cross | glassy | on | cross-on | cross-on | cross-on | on | on | on | on | cross-on | on | on |
High Tide | 5:14PM1.37m | 4:38AM1.44m | 5:32PM1.40m | 5:17AM1.43m | 5:51PM1.42m | 5:58AM1.39m | 6:10PM1.43m | 6:41AM1.32m | 6:31PM1.44m | 7:30AM1.23m | 6:53PM1.43m | 8:31AM1.12m | 7:17PM1.40m | ||||||||
Low Tide | 10:41AM0.20m | 10:51PM0.63m | 11:09AM0.24m | 11:22PM0.53m | 11:35AM0.32m | 11:54PM0.43m | 12:02PM0.43m | 00:30AM0.36m | 12:27PM0.56m | 1:09AM0.32m | 12:52PM0.70m | 1:54AM0.31m | 1:12PM0.84m | 2:52AM0.34m | |||||||
 |  |  | | |  | | | |  | |  | |  |  | | | | | | | |
 | 5:07 | — | — | 5:07 | — | — | 5:07 | — | — | 5:09 | — | — | 5:09 | — | — | 5:11 | — | — | 5:11 | — | — |
 | — | 6:12 | — | — | 6:09 | — | — | 6:08 | — | — | 6:07 | — | — | 6:06 | — | — | 6:05 | — | — | 6:04 | — |
mm | — | — | 1 | — | — | — | — | — | — | — | — | — | — | 1 | 3 | 4 | — | — | — | — | 1 |
Temp °C | 28 | 30 | 27 | 25 | 24 | 24 | 25 | 26 | 25 | 29 | 28 | 27 | 28 | 28 | 27 | 29 | 29 | 27 | 29 | 28 | 27 |
Feels °C | 27 | 30 | 32 | 24 | 23 | 24 | 28 | 30 | 28 | 31 | 29 | 30 | 31 | 31 | 30 | 30 | 31 | 30 | 30 | 29 | 27 |
Swell 1 Height (m) Direction Period (s) | S 8 | E 12 | SSW 6 | E 12 | E 11 | ENE 5 | E 11 | ESE 5 | E 5 | E 11 | ENE 6 | ESE 12 | ESE 11 | ESE 12 | ESE 11 | SE 6 | SE 6 | SE 7 | SE 7 | E 11 | SSE 6 |
| kJ | 84 | 103 | 34 | 67 | 63 | 33 | 59 | 22 | 18 | 37 | 23 | 129 | 229 | 288 | 226 | 66 | 109 | 97 | 97 | 85 | 74 |
Swell 2 Height (m) Direction Period (s) | E 12 | S 8 | E 12 | S 8 | SSW 7 | E 11 | SE 10 | E 11 | E 11 | E 5 | E 11 | S 11 | S 10 | S 10 | S 10 | ESE 11 | S 10 | SSW 10 | E 9 | SE 10 | SSW 10 |
| kJ | 151 | 46 | 99 | 18 | 18 | 58 | 25 | 61 | 56 | 8 | 57 | 58 | 75 | 100 | 98 | 161 | 130 | 136 | 44 | 15 | 82 |
Swell 3 Height (m) Direction Period (s) | SE 9 | SE 9 | S 8 | SE 11 | SE 11 | SE 10 | SSW 8 | SE 10 | SE 10 | SE 9 | SE 9 | ENE 6 | E 6 | NNE 8 | NNE 8 | S 10 | ESE 10 | ESE 10 | E 12 | E 16 | E 10 |
| kJ | 22 | 22 | 20 | 30 | 30 | 27 | 11 | 26 | 26 | 22 | 22 | 13 | 11 | 6 | 6 | 100 | 83 | 86 | 25 | 5 | 73 |
Wind waves Height (m) Direction Period (s) | SW 6 | SW 6 | — | NE 5 | ENE 5 | — | E 5 | — | SW 3 | SSW 4 | SSW 3 | S 3 | — | — | SE 5 | — | — | — | S 11 | S 6 | SSW 6 |
| kJ | 113 | 73 | — | 45 | 62 | — | 21 | — | 2 | 3 | 6 | 1 | — | — | 23 | — | — | — | 233 | 190 | 54 |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 23 | 23 | 0 | 132 | 56 | 0 | 0 | 0 | 2 | 0 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 143 | 1481 | 905 |
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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