Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 2 am 28 Aug 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
28.0°C
1.3° 

Onjuku surf forecast is for near shore open water. Breaking waves will often be smaller at less exposed spots.


Onjuku surf forecast from 27 Aug 2026:

  • Best quality surf: Friday 28 Aug, 9PM (local time) - 3ft (0.9m), 8s period, SSW swell with glassy winds.
  • Most powerful swell: Tuesday 1 Sep, 3PM (local time) - 3ft (0.9m), 12s period, ESE swell with 242 kJ wave energy.
  • Next surfable swell (1★+): Friday 28 Aug, 9PM (local time) - 3ft (0.9m), 8s period with SSW 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 Friday (Aug 28) at 9PM. The primary swell is predicted to be 0.6m and 12s period with a secondary swell of 0.9m and 8s. The wind is predicted to be glassy as the swell arrives.

The most powerful waves expected at Onjuku in the next 16 days are 0.9m 12s and forecast to arrive on Tuesday (Sep 01) at 3PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.1m 5s period and expected on Saturday (Aug 29) at 6PM.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+) 9PM (Fri 28th Aug)3ft (0.9m) 8s
Best Surf 9PM (Fri 28th Aug)3ft (0.9m) 8s
Most Powerful 3PM (Tue 1st Sep)3ft (0.9m) 12s

Table - best surf conditions forecast for Onjuku over the next 16 days.


The Lowdown

Alright, let’s get into it. The next couple of weeks are gonna be a real mixed bag here at Onjuku. I won’t lie, there’s a pretty nasty run of lumpy, wind-affected days to start things off, but if you’re patient, there are a couple of moments that might just make it worth hanging in there.

The first real window is on Friday morning, August 28th. But honestly, it’s not good. We’ve got a weak 0.7m easterly swell with a short period and a fresh cross-onshore wind from the WSW at 30 km/h. The water’s a touch warmer than normal at 28°, which is nice, but the waves are a mess—lumpy and just poor. Energy is weak, sitting at 291. Skip it.

That afternoon, the swell bumps up to 1.6m from the SW, but the period drops to a terrible 6 seconds, and we’ve only got a gentle cross-shore wind. The combined energy is moderate at 423, but direction, period, and a questionable tide mean it’s still only marginal at best.

The rest of that weekend and into the start of the week–Saturday 29th through Monday 31st–is a write-off. Tiny waves (0.4m to 0.6m), mostly onshore or cross-off winds, and just plain poor surf conditions. There’s a brief moment Sunday afternoon with glassy conditions, but the swell is only 0.5m, so you’re chasing ankle-biters.

We finally see a change on Friday, September 4th. The morning brings a clean 0.8m swell from the south, with a light cross-off breeze from the NNE at 10 km/h. Combined energy is a moderate 239. It’s not big, but the conditions are good, the wind is right, and it looks surfable. That afternoon gets even better—glassy conditions with just a whisper of wind from the ENE at 5 km/h. The swell drops slightly to 0.7m, but glassy conditions at Onjuku are rare and special. This is a solid “go surf” window, even if the waves are small.

Now, things get a bit wild. On Sunday, September 6th, a big pulse of south swell hits: 1.8m with a 14-second period. The combined energy jumps into the very strong range (1287). But the wind is a fresh cross-onshore from the SW at 30 km/h. That’s going to turn it into a choppy, lumpy mess. It’s heavy energy, but the wind ruins it. Monday the 7th is the same story—2.0m to 2.2m of south swell, but still cross-onshore or onshore wind. That kind of size with that wind makes for a difficult, scrubby session. Honestly, this setup might be more interesting for kite surfing than paddle surfing.

The absolute standout, the one to mark on your calendar, is Friday morning, September 11th. After a brutal run of poor conditions, we get a glassy morning with a 1.5m south swell, a 9-second period, and a whisper of WNW wind at just 5 km/h. Combined energy is a solid 419. This is the best combination of size and clean conditions in the whole 16-day window. It’s going to be overhead, clean, and glassy. Get in the water early before the wind picks up and swings onshore that afternoon.

Saturday morning, September 12th, is also worth a look. A clean 0.8m groundswell from the south, light cross-off wind from the ENE, and good conditions. Energy is moderate at 205. It’s smaller than Friday, but still clean.

Overall, the first week is a slog with onshore winds and poor quality. The small windows around September 4th and September 12th are nice, but Friday, September 11th is the one. It’s a proper glassy day with real swell. Don’t sleep on it.

Rusty

Short Range Forecast

Mostly dry. Warm (max 29°C on Fri afternoon, min 23°C on Sat night). Mainly fresh winds.

Days 4-6 Weather Summary

Light rain (total 2mm), mostly falling on Tue morning. Warm (max 28°C on Mon morning, min 26°C on Mon night). Wind will be generally light.

Friday
28
Saturday
29
Sunday
30
Monday
31
Tuesday
1
Wednesday
2
Thursday
3
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
0
1
2
0
0
0
1
1
1
0
0
0
1
0
0
0
0
0
0
0
0
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
0.7
E
12
1.6
SW
6
0.6
E
12
0.6
E
11
0.5
E
11
0.5
E
11
0.5
E
11
0.5
E
11
0.5
E
11
0.4
E
11
0.4
E
11
0.7
ESE
12
0.8
ESE
11
0.9
ESE
12
0.9
ESE
11
0.8
S
10
0.8
S
11
1.4
SE
7
0.9
SSW
11
1
S
11
0.9
SSW
11
Wave Graph
Metric surfscale
Energy kJ
148
213
99
94
59
58
59
61
56
37
37
129
133
242
210
138
146
189
194
229
198
Wind (km/h)
30
WSW
15
W
15
NE
25
ENE
20
ENE
15
NNE
15
N
5
N
0
WSW
15
SW
20
SSW
15
SSW
10
SE
15
SE
10
SE
10
S
20
S
25
SSW
25
SW
30
SSW
20
SW
Wind State
cross-on
cross
cross-off
cross-off
cross-off
cross-off
off
glassy
glassy
cross-on
cross-on
cross-on
cross-on
cross-on
cross-on
on
on
cross-on
cross-on
cross-on
cross-on
High Tide
5:14PM1.37m
4:38AM1.44m
5:32PM1.40m
5:17AM1.43m
5:51PM1.42m
5:58AM1.39m
6:10PM1.43m
6:41AM1.32m
6:31PM1.44m
7:30AM1.23m
6:53PM1.43m
8:31AM1.12m
7:17PM1.40m
Low Tide
10:41AM0.20m
10:51PM0.63m
11:09AM0.24m
11:22PM0.53m
11:35AM0.32m
11:54PM0.43m
12:02PM0.43m
00:30AM0.36m
12:27PM0.56m
1:09AM0.32m
12:52PM0.70m
1:54AM0.31m
1:12PM0.84m
2:52AM0.34m
cloud
part cloud
cloud
cloud
cloud
cloud
cloud
part cloud
part cloud
clear
clear
clear
rain showers
clear
thunderstorm
clear
clear
clear
clear
clear
clear
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
5:07
5:07
5:07
5:09
5:09
5:11
5:11
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
6:12
6:09
6:08
6:07
6:06
6:05
6:04
 mm
1
1
Temp °C
28
29
26
26
25
23
25
25
25
28
28
26
28
28
27
28
28
27
29
29
27
Feels °C
28
30
31
25
25
23
28
28
29
31
29
29
31
31
31
32
30
28
29
30
30
  • Map Icons:
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  • Live Wave Height (m)
  • Live Wind Speed (km/h)
  • Surf Rating (10 Max)
  • Ocean Swells (m)
  • Wind Speed (km/h)
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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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