
Surf Forecasts:
Onjuku surf forecast from 8 Sep 2026:
- Best quality surf: Wednesday 9 Sep, 6PM (local time) - 6.5ft (2.0m), 9s period, S swell with cross-offshore winds.
- Most powerful swell: Wednesday 9 Sep, 9AM (local time) - 8ft (2.4m), 8s period, S swell with 802 kJ wave energy.
- Next surfable swell (1★+): Wednesday 9 Sep, 6PM (local time) - 6.5ft (2.0m), 9s 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 Wednesday (Sep 09) at 6PM. The primary swell is predicted to be 2.0m and 9s period with a secondary swell of 0.2m and 16s. Another secondary swell of 0.5m and 9s is also forecast. 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 8s and forecast to arrive on Wednesday (Sep 09) 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 1.2m 6s period and expected on Friday (Sep 11) at 6PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Wed 9th Sep) | 6.5ft (2.0m) 9s |
| Best Surf | 6PM (Wed 9th Sep) | 6.5ft (2.0m) 9s |
| Most Powerful | 9AM (Wed 9th Sep) | 8ft (2.4m) 8s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s get into it.
First off, things are looking pretty grim around Onjuku for the next week or so. We’ve got a big storm blowing through Wednesday the 9th with strong, messy cross-onshore winds and a choppy 8 ft swell from the south – that’s a write-off. Thursday the 10th cleans up a bit with a cross-offshore breeze, but the swell drops to 5 ft from the northeast and the period is a short, weak 7 seconds, so it’s flat and uninspiring.
Friday the 11th is the first real flicker of hope. We get a moderate offshore wind from the NNE, which is a major positive for clean conditions. The morning swell is a small 4 ft from the ENE, but it’s clean. The afternoon drops right off to 2 ft, but here’s the kicker – that little wave has a very long 14-second period, meaning it’s a groundswell with serious energy for its size. The combined energy is weak (279), but a long-period groundswell like that will wrap into the beach break offering some oddly shaped, fun little lines if you’re on a log. The wind stays offshore, so it’ll be glassy.
Saturday the 12th and Sunday the 13th are marginal. Clean conditions with cross-offshore winds, but the swell is tiny (2 ft to 3 ft) and the period drops back to 9-13 seconds. The energy is very low (185-240). It’s surfable on a longboard, but you’ll be scratching for anything with shape.
Monday the 14th and Tuesday the 15th see a bit more size (3 ft to 4 ft), but the wind turns onshore or cross-onshore, and the period drops to 8-9 seconds, making it choppy and messy. Not worth paddling out.
The real standout, and the one you’ve been waiting for, is way out there on Wednesday the 23rd and Thursday the 24th of September. This is a long-range call, so it’s promising but not locked in yet. The wind is forecast to be a clean cross-offshore from the NE, and the swell really cranks up. On Wednesday the 23rd, we’re looking at a 7 ft to 8 ft S swell with a very long 16-17 second period. The combined energy jumps to a massive 2417-3294, which is strong wave energy. This is a proper groundswell. On Thursday the 24th, it gets even bigger – 10 ft from the south with a 17-second period and energy at 5947. That’s a very strong pulse. Because it’s a long-period groundswell, it will be powerful and clean, but a 10 ft wave at a beach break like Onjuku is only for experienced surfers. It might be too straight for the average punter, but the offshore wind will keep it looking good. This is the best on offer in the entire 16-day window.
For the rest of the second week, from the 18th to the 22nd, it’s mostly small (2 ft to 5 ft) and clean or cross-offshore, but the swell periods are short (5-11 seconds) and the energy is low (130-426). The 19th and 20th have 5 ft to 5 ft NE swell, but it’s still just a weak, short-period windswell. Nothing to get excited about.
Overall, the next week is a write-off, but the 23rd and 24th look like a serious, powerful groundswell event. Keep an eye on it.
Rusty.
Short Range ForecastHeavy rain (total 30mm), heaviest during Wed afternoon. Warm (max 29°C on Wed morning, min 20°C on Wed night). Mainly strong winds. | Days 5-7 Weather SummaryMostly dry. Warm (max 27°C on Mon morning, min 21°C on Fri night). Wind will be generally light. | ||||||||||||||||||
Wednesday 9 | Thursday 10 | Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | ||||||||||||||
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 8 | S 8 | S 9 | S 9 | NE 7 | NE 7 | ENE 8 | ENE 7 | NE 7 | E 14 | E 14 | E 13 | E 13 | SE 9 | SE 9 | SE 9 | SE 9 | SE 9 | SE 9 |
Wave Graph | |||||||||||||||||||
535 | 802 | 753 | 343 | 240 | 204 | 256 | 124 | 101 | 138 | 134 | 128 | 173 | 99 | 125 | 118 | 166 | 230 | 189 | |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | cross-on | cross-off | cross-off | cross-off | cross-off | off | off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | cross-off | on | on | on |
High Tide | 2:06AM1.33m | 4:14PM1.34m | 3:06AM1.40m | 4:32PM1.36m | 3:56AM1.45m | 4:50PM1.39m | 4:41AM1.47m | 5:08PM1.41m | 5:24AM1.44m | 5:26PM1.43m | 6:04AM1.38m | 5:44PM1.44m | |||||||
Low Tide | 9:17AM0.17m | 9:34PM0.80m | 9:55AM0.18m | 10:07PM0.64m | 10:29AM0.24m | 10:40PM0.50m | 10:59AM0.34m | 11:13PM0.38m | 11:26AM0.45m | 11:46PM0.30m | 11:50AM0.57m | 00:19AM0.26m | |||||||
— | 5:16 | — | — | 5:16 | — | — | 5:16 | — | — | 5:18 | — | — | 5:18 | — | — | 5:18 | — | — | |
— | — | 5:54 | — | — | 5:53 | — | — | 5:52 | — | — | 5:51 | — | — | 5:49 | — | — | 5:47 | — | |
mm | 7 | 2 | 5 | 8 | 2 | 2 | 3 | 1 | — | — | — | — | — | — | — | — | — | — | 4 |
Temp °C | 27 | 29 | 29 | 23 | 20 | 21 | 20 | 20 | 20 | 21 | 23 | 23 | 23 | 24 | 25 | 25 | 27 | 27 | 26 |
Feels °C | 27 | 29 | 30 | 22 | 16 | 19 | 18 | 20 | 20 | 21 | 22 | 23 | 24 | 25 | 27 | 29 | 30 | 29 | 28 |
Swell 1 Height (m) Direction Period (s) | E 8 | ESE 10 | NE 8 | S 9 | S 8 | S 8 | S 8 | S 8 | S 8 | S 8 | E 14 | E 13 | E 13 | SE 9 | SE 9 | SE 9 | SE 9 | SE 9 | SE 9 |
31 | 10 | 11 | 343 | 171 | 132 | 82 | 78 | 57 | 55 | 134 | 128 | 173 | 99 | 110 | 118 | 166 | 230 | 189 | |
Swell 2 Height (m) Direction Period (s) | SE 10 | NE 9 | E 16 | ESE 16 | ESE 15 | ESE 15 | ESE 14 | E 14 | E 14 | E 14 | S 7 | SE 9 | SE 9 | E 13 | E 13 | E 12 | E 12 | E 12 | E 13 |
15 | 12 | 21 | 49 | 42 | 72 | 67 | 106 | 101 | 138 | 28 | 39 | 41 | 86 | 125 | 76 | 110 | 77 | 170 | |
Swell 3 Height (m) Direction Period (s) | NNE 8 | E 17 | E 16 | SE 9 | SE 9 | SE 9 | SE 9 | SE 9 | SE 10 | SE 9 | SE 9 | SSW 7 | SSW 7 | SSW 7 | SSW 7 | ENE 6 | ENE 6 | NE 6 | S 7 |
6 | 23 | 46 | 14 | 14 | 22 | 14 | 13 | 24 | 21 | 39 | 18 | 9 | 5 | 5 | 14 | 14 | 10 | 1 | |
Wind waves Height (m) Direction Period (s) | S 8 | S 8 | S 9 | NE 7 | NE 7 | NE 7 | ENE 8 | ENE 7 | NE 7 | NE 6 | NE 6 | NE 6 | NE 6 | NE 6 | ENE 6 | — | — | — | SW 7 |
535 | 802 | 753 | 296 | 240 | 204 | 256 | 124 | 97 | 78 | 73 | 49 | 45 | 38 | 32 | — | — | — | 2 | |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 557 | 574 | 75 | 110 | 206 | 110 | 73 | 0 | 0 | 16 | 56 | 56 | 56 | 56 | 56 | 0 | 9 | 9 | 9 |
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.










