Surf Forecasts:
Onjuku surf forecast from 21 Aug 2026:
- Best quality surf: Monday 24 Aug, 9AM (local time) - 4.5ft (1.3m), 19s period, SSE swell with glassy winds.
- Most powerful swell: Tuesday 25 Aug, 12AM (local time) - 7.5ft (2.3m), 15s period, SSE swell with 2,258 kJ wave energy.
- Next surfable swell (1★+): Saturday 22 Aug, 9PM (local time) - 3.5ft (1.0m), 10s 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 Saturday (Aug 22) at 9PM. The primary swell is predicted to be 1.0m and 10s period with a secondary swell of 0.5m and 5s. 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 2.3m 15s and forecast to arrive on Tuesday (Aug 25) at 12AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 4s period and expected on Sunday (Aug 23) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Sat 22nd Aug) | 3.5ft (1.0m) 10s |
| Best Surf | 9AM (Mon 24th Aug) | 4.5ft (1.3m) 19s |
| Most Powerful | 12AM (Tue 25th Aug) | 7.5ft (2.3m) 15s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright, Rusty here. Let's have a look at what's on the menu for our little corner of the coast.
Right off the bat, we're in a bit of a flat spell. The first solid surf recommendation isn't until Monday the 24th of August, so we've got a few days of small, choppy, and generally poor conditions to sit through. The water temp is sitting right around 80° with hardly any difference from normal, so it's about as average as it gets for this time of year – no surprises there.
The real standout, and I mean the one to circle on the calendar, is Monday morning the 24th of August at Onjuku. The conditions are shaping up to be excellent. We're looking at a clean 5ft swell from the SSE with a solid 18-second period. That's a proper long-period groundswell, bringing a heap of energy (1750) and good shape. The wind is forecast to be glassy – dead calm – which means the surface will be like a mirror. For experienced surfers, this is the pick of the window. The SSE direction is right on the money for what this spot likes. Just keep in mind it's inconsistent, so you'll have to be patient between sets, and it can get crowded sometimes.
We get another window of interest on Thursday the 3rd of September. The afternoon looks best, with a very clean 8ft swell from the SE, again with a long 16-second period. The energy is strong (4414), and with a light cross-off breeze, it'll be clean. This is a big swell, so it's for the more experienced crew. The following morning, Friday the 4th, is actually a little too big for Onjuku, with a 13ft swell predicted. The forecast calls it too big for the break, so that's a pass for us, even though it's clean.
The rest of the period is a mix of marginal and poor conditions, with a lot of onshore wind and choppy surf. Sunday the 30th of August has some clean conditions but with tiny 3ft swell and hardly any energy. Not worth paddling out for.
So, to break it down: the first week is a write-off. The absolute best bet is Monday the 24th of August. After that, keep an eye on Thursday the 3rd of September for another solid, clean groundswell for the experienced surfer. The rest is for the kites on windy days.
Rusty.
Short Range ForecastModerate rain (total 10mm), heaviest on Sat night. Warm (max 28°C on Sat morning, min 23°C on Sat night). Wind will be generally light. | Days 5-7 Weather SummaryLight rain (total 3mm), mostly falling on Wed night. Warm (max 28°C on Tue morning, min 25°C on Mon night). Wind will be generally light. | |||||||||||||||||||
Fri 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | Thursday 27 | ||||||||||||||
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) | SE 10 | E 9 | E 11 | E 11 | E 10 | E 9 | SSE 12 | SSE 12 | SSE 19 | SSE 16 | SSE 15 | SSE 13 | S 14 | S 13 | S 12 | S 13 | SSW 12 | S 9 | S 9 | S 9 |
Wave Graph  | ||||||||||||||||||||
 kJ | 39 | 41 | 151 | 233 | 161 | 83 | 104 | 196 | 1159 | 2107 | 2258 | 1077 | 1807 | 1228 | 513 | 408 | 164 | 210 | 282 | 235 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-on | cross-on | cross-on | off | cross-off | cross-off | off | glassy | on | cross-on | cross-on | on | on | cross-on | on | on | on | on | on |
High Tide | 8:35PM1.27m | 9:35PM1.21m | 4:31PM1.15m | 11:58PM1.18m | 4:19PM1.20m | 1:32AM1.23m | 4:27PM1.25m | 2:31AM1.30m | 4:41PM1.29m | 3:17AM1.37m | 4:57PM1.33m | |||||||||
Low Tide | 6:00AM0.49m | 7:29AM0.43m | 7:50PM1.12m | 8:27AM0.35m | 8:48PM1.04m | 9:08AM0.28m | 9:22PM0.95m | 9:42AM0.22m | 9:51PM0.85m | 10:12AM0.19m | 10:21PM0.74m | |||||||||
 |  |  | | | | |  |  | |  | | | | | |  | | | | |
 | — | — | 5:01 | — | — | 5:03 | — | — | 5:03 | — | — | 5:05 | — | — | 5:05 | — | — | 5:05 | — | — |
 | 6:21 | — | — | 6:19 | — | — | 6:17 | — | — | 6:16 | — | — | 6:15 | — | — | 6:14 | — | — | 6:13 | — |
mm | — | 1 | 1 | 3 | 5 | — | — | — | — | — | — | — | — | — | — | — | 1 | 2 | 3 | 8 |
Temp °C | 27 | 26 | 28 | 28 | 25 | 26 | 26 | 25 | 27 | 27 | 26 | 28 | 28 | 27 | 28 | 28 | 27 | 28 | 28 | 26 |
Feels °C | 28 | 28 | 30 | 30 | 29 | 28 | 28 | 29 | 29 | 29 | 28 | 30 | 30 | 30 | 31 | 30 | 29 | 29 | 29 | 27 |
Swell 1 Height (m) Direction Period (s) | E 8 | E 9 | E 11 | E 11 | E 10 | E 9 | E 9 | SSE 12 | SSE 19 | SSE 16 | SSE 15 | SSE 13 | S 14 | S 13 | S 12 | S 13 | SSE 9 | E 14 | E 14 | E 13 |
| kJ | 35 | 41 | 151 | 233 | 161 | 83 | 60 | 196 | 1159 | 2107 | 2258 | 1077 | 1807 | 1228 | 513 | 408 | 99 | 153 | 232 | 222 |
Swell 2 Height (m) Direction Period (s) | S 8 | SSW 9 | S 5 | S 5 | S 5 | SSW 9 | SSE 12 | ENE 9 | SSE 12 | E 12 | E 11 | S 15 | ESE 13 | ESE 13 | SSE 11 | ESE 12 | SSW 12 | SSW 11 | SW 11 | SE 14 |
| kJ | 36 | 25 | 22 | 17 | 7 | 15 | 104 | 82 | 222 | 134 | 89 | 780 | 184 | 176 | 218 | 113 | 164 | 49 | 29 | 8 |
Swell 3 Height (m) Direction Period (s) | SE 10 | SE 10 | SSW 9 | SSW 9 | SSW 9 | SE 10 | ESE 12 | ESE 12 | E 12 | ESE 15 | ESE 15 | ESE 14 | SW 10 | E 19 | ESE 12 | E 16 | E 12 | ESE 10 | SE 13 | SSE 9 |
| kJ | 39 | 36 | 28 | 27 | 26 | 16 | 56 | 50 | 172 | 47 | 42 | 198 | 16 | 7 | 117 | 46 | 70 | 33 | 7 | 35 |
Wind waves Height (m) Direction Period (s) | S 3 | S 4 | SSW 5 | SSW 5 | NE 3 | NE 4 | ENE 4 | — | — | SSW 10 | SSW 10 | — | — | — | — | S 10 | S 5 | S 9 | S 9 | S 9 |
| kJ | 6 | 24 | 31 | 24 | 3 | 10 | 10 | — | — | 81 | 63 | — | — | — | — | 221 | 30 | 210 | 282 | 235 |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 9 | 142 | 17 | 17 | 0 | 16 | 56 | 0 | 0 | 9 | 23 | 17 | 9 | 9 | 88 | 9 | 9 | 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.
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