Surf Forecasts:
Onjuku surf forecast from 18 Aug 2026:
- Best quality surf: Sunday 23 Aug, 12AM (local time) - 3.5ft (1.0m), 10s period, E swell with offshore winds.
- Most powerful swell: Wednesday 26 Aug, 9AM (local time) - 8ft (2.5m), 17s period, S swell with 4,173 kJ wave energy.
- Next surfable swell (1★+): Wednesday 19 Aug, 6AM (local time) - 2ft (0.6m), 8s 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 Wednesday (Aug 19) at 6AM. The primary swell is predicted to be 0.6m and 8s period with a secondary swell of 0.6m and 6s. The wind is predicted to be glassy as the swell arrives.
The most powerful waves expected at Onjuku in the next 16 days are 2.5m 17s and forecast to arrive on Wednesday (Aug 26) 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 0.7m 4s period and expected on Sunday (Aug 23) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6AM (Wed 19th Aug) | 2ft (0.6m) 8s |
| Best Surf | 12AM (Sun 23rd Aug) | 3.5ft (1.0m) 10s |
| Most Powerful | 9AM (Wed 26th Aug) | 8ft (2.5m) 17s |
Table - best surf conditions forecast for Onjuku over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let's break down what's shakin' for Onjuku over the next couple weeks.
Truth be told, the first week-plus is a grind. We've got persistent cross-onshore wind and small, weak, junky swell. The first real chance of a wave comes on Sunday, August 23rd. That morning, the wind goes glassy, and we get a clean 3ft east swell with moderate energy. It's not gonna blow your mind, but it'll be clean and rideable. Just remember, this spot is inconsistent, so you'll be waiting between sets.
After that, it's back to poor conditions until Tuesday, August 25th. Tuesday morning brings a clean 2-3ft swell from the ESE with a very long 14-second period and light onshore wind. That's real groundswell energy, so it'll have good punch, but at a beach break it might wall up a bit.
Now for the big one, and I mean *big*. Sunday, August 30th. Onjuku gets absolutely slammed with a 12ft SE swell. The energy readings are insane. The wind is cross-shore and then cross-offshore, and the conditions get clean. HOWEVER – and this is critical – 12ft is massive. This is expert-only territory. Beginners, don't even think about it. If you've got the skill, this is the best setup of the whole forecast, but it's a long way out, so keep your hopes in check.
That huge swell sticks around into early September, still over 10ft with offshore or clean sideshore winds on the 1st and 2nd. Same story – experts only.
So, the call: the standout is that massive SE groundswell kicking off around August 30th. It's big, it's clean, it's powerful. Everything before that is small, inconsistent, or blown out. For the average surfer, that glassy 3ft day on the 23rd is your only solid bet.
This is Rusty, signing off.
Short Range ForecastSome drizzle, heaviest during Fri night. Warm (max 28°C on Fri morning, min 25°C on Wed night). Wind will be generally light. | Days 4-6 Weather SummaryMostly dry. Warm (max 29°C on Sat morning, min 24°C on Sat night). Wind will be generally light. | ||||||||||||||||||||
Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | |||||||||||||||
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) | SE 10 | E 9 | E 9 | SE 10 | SE 11 | SE 11 | S 9 | SE 10 | E 9 | E 11 | E 10 | E 10 | E 10 | E 9 | E 9 | E 12 | SSE 14 | SSE 17 | SSE 15 | SSE 14 | SSE 15 |
Wave Graph  | |||||||||||||||||||||
 kJ | 35 | 36 | 37 | 39 | 40 | 40 | 40 | 39 | 58 | 151 | 221 | 198 | 120 | 80 | 78 | 69 | 186 | 427 | 1432 | 1598 | 2688 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | cross-on | cross-on | on | on | on | on | cross-on | cross-on | cross-on | off | cross-off | cross-off | off | glassy | on | cross-on | cross-on | cross-on | cross-on |
High Tide | 7:42PM1.36m | 9:58AM0.96m | 8:05PM1.32m | 8:35PM1.27m | 9:35PM1.21m | 4:31PM1.15m | 11:58PM1.18m | 4:19PM1.20m | 1:32AM1.23m | 4:27PM1.25m | 2:31AM1.30m | ||||||||||
Low Tide | 1:24PM0.80m | 3:09AM0.46m | 1:21PM0.89m | 4:20AM0.49m | 6:00AM0.49m | 7:29AM0.43m | 7:50PM1.12m | 8:27AM0.35m | 8:48PM1.04m | 9:08AM0.28m | 9:22PM0.95m | ||||||||||
 |  |  | | |  | | |  | | | | | | | | | | | | | |
 | 5:00 | — | — | 5:01 | — | — | 5:01 | — | — | 5:01 | — | — | 5:03 | — | — | 5:03 | — | — | 5:05 | — | — |
 | — | 6:22 | — | — | 6:22 | — | — | 6:21 | — | — | 6:19 | — | — | 6:17 | — | — | 6:16 | — | — | 6:15 | — |
mm | — | — | — | — | — | — | — | — | 1 | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 27 | 27 | 26 | 27 | 27 | 26 | 28 | 27 | 26 | 29 | 29 | 26 | 26 | 26 | 25 | 27 | 28 | 26 | 28 | 28 | 26 |
Feels °C | 30 | 29 | 29 | 30 | 29 | 29 | 29 | 28 | 28 | 30 | 30 | 29 | 29 | 28 | 28 | 32 | 30 | 28 | 27 | 27 | 28 |
Swell 1 Height (m) Direction Period (s) | SE 6 | SE 6 | SE 6 | SE 6 | E 8 | E 8 | E 8 | E 8 | E 9 | E 11 | E 10 | E 10 | E 10 | E 9 | E 9 | E 9 | SSE 14 | SSE 13 | SSE 15 | SSE 14 | SSE 15 |
| kJ | 23 | 21 | 20 | 15 | 33 | 32 | 34 | 35 | 58 | 151 | 221 | 198 | 120 | 80 | 78 | 55 | 186 | 427 | 1432 | 1598 | 2688 |
Swell 2 Height (m) Direction Period (s) | E 8 | E 9 | E 9 | E 8 | SE 11 | SE 11 | S 9 | S 8 | S 9 | SSW 9 | SSW 9 | S 5 | S 5 | SE 11 | E 12 | SE 11 | E 8 | SSE 17 | ESE 14 | ESE 13 | E 13 |
| kJ | 35 | 36 | 37 | 21 | 40 | 40 | 39 | 36 | 39 | 28 | 27 | 12 | 7 | 30 | 73 | 55 | 50 | 404 | 254 | 232 | 166 |
Swell 3 Height (m) Direction Period (s) | SE 10 | SE 10 | SE 10 | SE 10 | SSW 9 | SSW 8 | SE 11 | SE 10 | SE 10 | SE 10 | SSE 11 | SSW 9 | SSW 9 | ESE 12 | SSE 10 | E 12 | SSE 12 | E 11 | SW 11 | SSW 10 | SSW 10 |
| kJ | 35 | 35 | 35 | 39 | 16 | 13 | 40 | 39 | 36 | 25 | 12 | 28 | 15 | 48 | 39 | 69 | 91 | 114 | 29 | 11 | 11 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | SE 5 | SSE 5 | SSE 5 | S 3 | S 5 | S 5 | SSW 4 | — | NE 4 | ENE 4 | — | — | — | — | — | SW 11 | — |
| kJ | — | — | — | — | 10 | 5 | 4 | 3 | 16 | 24 | 24 | — | 16 | 15 | — | — | — | — | — | 115 | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 17 | 9 | 23 | 0 | 0 | 0 | 0 | 0 | 9 | 88 | 88 | 557 | 88 |
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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