Surf Forecasts:
Onjuku surf forecast from 4 Sep 2026:
- Best quality surf: Tuesday 8 Sep, 9AM (local time) - 11ft (3.5m), 10s period, S swell with cross-onshore winds.
- Most powerful swell: Monday 7 Sep, 12PM (local time) - 13ft (4.0m), 11s period, SSE swell with 3,745 kJ wave energy.
- Next surfable swell (1★+): Tuesday 8 Sep, 9AM (local time) - 11ft (3.5m), 10s period with S 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 (Sep 08) at 9AM. The primary swell is predicted to be 3.5m and 10s period with a secondary swell of 2.5m and 10s. Another secondary swell of 0.6m and 8s is also forecast. The wind is predicted to be cross-onshore as the swell arrives.
The most powerful waves expected at Onjuku in the next 16 days are 4.0m 11s and forecast to arrive on Monday (Sep 07) at 12PM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.6m 6s period and expected on Saturday (Sep 05) at 6AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9AM (Tue 8th Sep) | 11ft (3.5m) 10s |
| Best Surf | 9AM (Tue 8th Sep) | 11ft (3.5m) 10s |
| Most Powerful | 12PM (Mon 7th Sep) | 13ft (4.0m) 11s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright, Rusty here. Let's chat about what's on the table for Onjuku over the next couple of weeks.
Right off the bat, this is a mixed bag of a forecast. The first few days are pretty grim, with rain and strong onshore winds making a mess of things, and the water temp is sitting at a balmy 81.5°F, which is about 1.8°F warmer than average for this time of year. Nothing to get excited about there for a while.
The first real chance for a surf comes around early next week. On Tuesday, September 8th, there’s a big pulse of swell forecasted. The morning is a write-off with a strong cross-onshore wind, but Tuesday afternoon? That’s the standout. The wind swings around to a light cross-off from the NNW, cleaning things right up for a solid 9.8ft swell rolling in from the S. The period is a long 10 seconds, packing some serious punch. This is not for the faint-hearted as it's well over 8ft, so only for experienced surfers, but the conditions will be excellent for them.
Wednesday morning, September 9th, will still have some solid leftover swell - 7.9ft from the S - with clean, cross-off winds from the NW, offering another good morning for the crew with some skills. By the afternoon, the swell drops to 7.2ft and the wind goes straight offshore from the N at 12 mph, which will be very good, clean waves.
After that, the swell drops off a cliff. From Thursday the 10th right through to the end of the forecast, we’re looking at small, weak surf. Periods of 6 to 8 seconds and heights mostly under 3ft mean it’s a long stretch of marginal to poor conditions. There is a brief moment on Saturday, September 12th, with a silky glassy morning and a tiny 2ft groundswell from the ESE with a very long 14-second period, but the energy is low. Good for a longboard if you're desperate, but hardly a call-to-arms. The rest is just wind chop and small junk.
To be honest, the only window that really stands out is that Tuesday afternoon and Wednesday morning of September 8th and 9th. That’s the only time we get size and clean conditions together.
Short Range ForecastHeavy rain (total 201mm), heaviest during Sun night. Warm (max 27°C on Mon morning, min 22°C on Fri night). Winds increasing (light winds from the ENE on Fri afternoon, strong winds from the SSE by Sun night). | Days 5-7 Weather SummaryHeavy rain (total 70mm), heaviest during Wed afternoon. Warm (max 27°C on Mon afternoon, min 21°C on Thu morning). Winds decreasing (fresh winds from the SSW on Mon afternoon, calm by Tue night). | |||||||||||||||||||
Fri 4 | Saturday 5 | Sunday 6 | Monday 7 | Tuesday 8 | Wednesday 9 | Thursday 10 | ||||||||||||||
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) | S 10 | S 9 | E 6 | E 6 | SSW 8 | ENE 7 | ENE 7 | E 8 | SSE 9 | SSE 11 | S 11 | S 10 | S 10 | S 10 | S 10 | S 10 | S 9 | S 9 | ENE 7 | ENE 7 |
Wave Graph  | ||||||||||||||||||||
 kJ | 70 | 61 | 200 | 109 | 23 | 374 | 489 | 816 | 2249 | 2588 | 2973 | 2137 | 1509 | 1601 | 1102 | 891 | 449 | 239 | 310 | 210 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-on | on | on | cross-on | cross-on | cross-off | cross-off | cross-off | off | cross-off | cross-off | cross-off | cross-off |
High Tide | 7:46PM1.36m | 8:26PM1.30m | 4:09PM1.19m | 10:16PM1.23m | 3:44PM1.25m | 00:42AM1.25m | 3:57PM1.30m | 2:06AM1.33m | 4:14PM1.34m | 3:06AM1.40m | 4:32PM1.36m | |||||||||
Low Tide | 4:13AM0.36m | 6:01AM0.34m | 6:12PM1.19m | 7:30AM0.27m | 8:17PM1.09m | 8:30AM0.20m | 8:59PM0.95m | 9:17AM0.17m | 9:34PM0.80m | 9:55AM0.18m | 10:07PM0.64m | |||||||||
 |  |  |  |  | |  | | | | | | |  | | |  |  | | | |
 | — | — | 5:13 | — | — | 5:13 | — | — | 5:13 | — | — | 5:15 | — | — | 5:16 | — | — | 5:16 | — | — |
 | 6:01 | — | — | 6:00 | — | — | 5:59 | — | — | 5:58 | — | — | 5:57 | — | — | 5:54 | — | — | 5:53 | — |
mm | 1 | 25 | 8 | 3 | 4 | 6 | 20 | 103 | 31 | 5 | 7 | 7 | 3 | 11 | 12 | 19 | 1 | 5 | 5 | 17 |
Temp °C | 26 | 24 | 23 | 22 | 23 | 23 | 24 | 26 | 27 | 27 | 27 | 27 | 24 | 26 | 23 | 23 | 23 | 22 | 21 | 20 |
Feels °C | 28 | 26 | 23 | 20 | 21 | 19 | 24 | 25 | 26 | 26 | 27 | 31 | 28 | 27 | 25 | 24 | 22 | 19 | 18 | 18 |
Swell 1 Height (m) Direction Period (s) | SE 6 | S 9 | S 10 | SSW 9 | SSW 8 | SSW 9 | S 8 | S 9 | ENE 9 | E 9 | SSE 11 | SSE 10 | SSE 10 | S 10 | S 10 | S 10 | S 9 | S 9 | S 9 | S 8 |
| kJ | 38 | 61 | 47 | 28 | 23 | 7 | 29 | 103 | 464 | 335 | 2130 | 1322 | 1064 | 1183 | 1102 | 891 | 449 | 230 | 119 | 84 |
Swell 2 Height (m) Direction Period (s) | S 10 | E 9 | ENE 13 | ENE 13 | E 12 | SSE 8 | SE 12 | S 11 | ESE 8 | — | E 9 | E 8 | E 8 | E 18 | E 17 | E 16 | ESE 16 | ESE 15 | ESE 14 | ESE 14 |
| kJ | 70 | 41 | 34 | 33 | 11 | 7 | 5 | 123 | 191 | — | 129 | 47 | 37 | 6 | 23 | 21 | 48 | 43 | 70 | 68 |
Swell 3 Height (m) Direction Period (s) | E 9 | SE 6 | SSE 9 | SE 9 | SSE 8 | SE 12 | SE 14 | — | — | — | — | NE 11 | E 19 | E 18 | E 9 | E 9 | SE 11 | SE 11 | ESE 11 | SE 10 |
| kJ | 41 | 19 | 8 | 12 | 7 | 6 | 8 | — | — | — | — | 4 | 7 | 25 | 15 | 15 | 5 | 5 | 11 | 15 |
Wind waves Height (m) Direction Period (s) | ESE 6 | ENE 4 | E 6 | E 6 | E 6 | ENE 7 | ENE 7 | E 8 | SSE 9 | SSE 11 | S 11 | S 10 | S 10 | S 10 | NE 8 | NE 5 | NE 6 | ENE 6 | ENE 7 | ENE 7 |
| kJ | 34 | 34 | 200 | 109 | 132 | 374 | 489 | 816 | 2249 | 2588 | 2973 | 2137 | 1509 | 1601 | 35 | 57 | 105 | 239 | 310 | 210 |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 0 | 51 | 206 | 56 | 536 | 617 | 617 | 617 | 84 | 200 | 88 | 18 | 0 | 0 | 0 | 0 | 51 | 51 | 553 | 82 |
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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