Surf Forecasts:
Onjuku surf forecast from 21 Aug 2026:
- Best quality surf: Monday 24 Aug, 6AM (local time) - 4ft (1.2m), 19s period, SSE swell with offshore winds.
- Most powerful swell: Monday 24 Aug, 3PM (local time) - 7ft (2.2m), 16s period, SSE swell with 2,214 kJ wave energy.
- Next surfable swell (1★+): Saturday 22 Aug, 6PM (local time) - 3.5ft (1.0m), 11s 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 6PM. The primary swell is predicted to be 1.0m and 11s period with a secondary swell of 0.7m and 5s. Another secondary swell of 0.8m and 5s is also forecast. The wind is predicted to be offshore as the swell arrives.
The most powerful waves expected at Onjuku in the next 16 days are 2.2m 16s and forecast to arrive on Monday (Aug 24) at 3PM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 3s period and expected on Sunday (Aug 23) at 12PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Sat 22nd Aug) | 3.5ft (1.0m) 11s |
| Best Surf | 6AM (Mon 24th Aug) | 4ft (1.2m) 19s |
| Most Powerful | 3PM (Mon 24th Aug) | 7ft (2.2m) 16s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright folks, Rusty here, let's talk about what's on the menu for Onjuku over the next couple of weeks.
It’s a bit of a slow start, I’m not gonna lie. We’ve got a few days of small, messy, onshore slop to get through first. The water temp is sitting pretty at 80°, which is bang on average for this time of year, so at least it’ll be a warm wait.
Friday the 21st and Saturday the 22nd are write-offs. Tiny little 1ft to 3ft SSE and E swells, but with a stiff cross-onshore wind, it’s just choppy and ugly. Not worth paddling out for.
Sunday the 23rd cleans up a bit with a cross-offshore breeze, but it’s still only 2ft to 3ft of short-period E swell. The morning is a no-go, and the afternoon is only getting a 1 out of 10, so it’s a pass for me.
The real story starts to unfold on Monday the 24th. That’s where we get our first true standout. Early morning, the wind goes glassy, dead calm. The swell jumps to 7ft from the SSE, with a super long 18-second period. That’s serious groundswell energy, and the combined energy is a massive 2516. This is fantastic for experienced surfers – it’s too big for beginners, but for those with the skills, it’s going to be excellent. The glassy conditions will make it absolutely perfect. Be aware that a long-period swell like this (18 seconds) can make the waves break a bit too straight at a beach break, but for a point or reef, it’s magic. The afternoon sees the wind swing onshore and the quality drops, so get it while you can.
Tuesday the 25th still has a solid 8ft swell from the SSE, but the wind is cross-onshore, making it choppy and less appealing. The energy is still high (2285), but the wind is the enemy here.
We get a bit of a lull on Wednesday and Thursday with dropping swell and persistent onshore winds, so nothing to get excited about.
Friday the 28th is a mess with strong 31 mph winds and lumpy, cross-onshore junk. Not a paddle session.
The next real window of opportunity appears on Sunday the 30th. The wind goes clean and cross-offshore, with a 4ft to 4ft SSE swell. The combined energy is a moderate 525, and the conditions are labeled as “very good.” This is a solid, fun-sized day for a wider range of surfers, with clean conditions. This is your second standout for the period.
Monday the 31st and Tuesday the 1st of September stay similar, with clean conditions and 4ft to 4ft swell, but the quality drops a notch. Still worth a look if you’re itching.
Then we get a massive warning. On Thursday the 3rd of September, the swell forecast goes nuclear. We’re looking at a 33ft swell from the ESE with a combined energy of 98121. The wind is offshore and clean, but the swell is absolutely colossal. This is not for anyone. This is a “stay on the beach and watch” kind of day. The same goes for the 4th of September with an 18ft swell. It’s just too big for Onjuku.
The run-up to the 5th of September shows the swell dropping back down to a more manageable 5ft to 7ft, but the wind is strong and cross-shore, so it’s still a messy prospect.
So, to wrap it up: the two clear standouts are the glassy, powerful groundswell on Monday morning the 24th, and the clean, fun-sized swell on Sunday the 30th. Everything else is either flat, windy, or dangerously oversized.
Signing off, Rusty.
Short Range ForecastLight rain (total 5mm), mostly falling on Sat afternoon. Warm (max 28°C on Sat morning, min 24°C on Sat night). Wind will be generally light. | Days 4-6 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. | ||||||||||||||||||||
Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | Wednesday 26 | Thursday 27 | |||||||||||||||
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) | S 9 | SE 10 | E 9 | E 11 | E 11 | E 10 | E 9 | SSE 12 | SSE 12 | SSE 18 | SSE 16 | SSE 15 | SSE 13 | S 14 | S 13 | S 12 | S 9 | SSE 9 | E 15 | E 14 | E 13 |
Wave Graph | |||||||||||||||||||||
40 | 39 | 41 | 151 | 233 | 161 | 83 | 104 | 193 | 1522 | 2214 | 1077 | 1616 | 1682 | 1070 | 425 | 287 | 144 | 155 | 232 | 229 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | on | cross-on | cross-on | cross-on | off | cross-off | cross-off | off | glassy | on | cross-on | cross-on | on | on | on | on | on | on | on | cross-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 | — | — | 5:01 | — | — | 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 | — | 3 | 1 | — | — | — | — | — | — | — | — | — | — | — | 3 | 6 | 7 | 13 |
Temp °C | 27 | 27 | 26 | 28 | 27 | 24 | 27 | 26 | 25 | 27 | 27 | 26 | 28 | 28 | 27 | 28 | 28 | 27 | 27 | 27 | 26 |
Feels °C | 29 | 28 | 27 | 29 | 29 | 27 | 29 | 27 | 28 | 30 | 29 | 28 | 31 | 31 | 31 | 30 | 29 | 29 | 27 | 27 | 28 |
Swell 1 Height (m) Direction Period (s) | E 8 | E 8 | E 9 | E 11 | E 11 | E 10 | E 9 | E 9 | SSE 12 | SSE 18 | SSE 16 | SSE 13 | SSE 13 | S 14 | S 13 | S 12 | SSW 12 | SSE 9 | SSE 9 | E 14 | E 13 |
34 | 35 | 41 | 151 | 233 | 161 | 83 | 80 | 193 | 1522 | 2214 | 878 | 1616 | 1682 | 1070 | 425 | 198 | 144 | 103 | 232 | 229 | |
Swell 2 Height (m) Direction Period (s) | S 9 | S 8 | SSW 9 | SSW 9 | SSW 9 | S 5 | SSW 9 | SSE 12 | E 9 | SSE 12 | E 12 | SSE 15 | ESE 14 | ESE 13 | ESE 13 | SSE 10 | ESE 12 | SSW 11 | E 15 | SSE 9 | SSE 9 |
39 | 36 | 25 | 28 | 27 | 11 | 15 | 104 | 56 | 177 | 137 | 1077 | 198 | 181 | 176 | 227 | 113 | 71 | 155 | 80 | 35 | |
Swell 3 Height (m) Direction Period (s) | SE 11 | SE 10 | SE 10 | SE 10 | SE 10 | SSW 9 | S 4 | ESE 12 | ESE 12 | E 8 | ESE 15 | E 11 | SW 10 | SW 10 | E 19 | ESE 12 | E 16 | E 12 | ESE 10 | SSW 9 | SSW 11 |
40 | 39 | 36 | 25 | 28 | 26 | 3 | 56 | 50 | 51 | 47 | 88 | 15 | 15 | 30 | 117 | 47 | 70 | 39 | 17 | 40 | |
Wind waves Height (m) Direction Period (s) | SSE 4 | S 4 | S 4 | S 5 | S 5 | NNE 3 | NE 4 | NE 4 | — | — | SSW 10 | SSW 9 | — | — | — | — | S 9 | S 5 | S 6 | S 6 | S 7 |
7 | 9 | 18 | 29 | 24 | 1 | 3 | 10 | — | — | 38 | 55 | — | — | — | — | 287 | 51 | 95 | 85 | 135 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 23 | 9 | 23 | 18 | 9 | 0 | 12 | 56 | 0 | 0 | 9 | 9 | 88 | 557 | 101 | 88 | 132 | 9 | 101 | 1295 | 557 |
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.











