Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 8 am 10 Sep 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
27.5°C
1.1° 

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


Onjuku surf forecast from 10 Sep 2026:

  • Best quality surf: Friday 11 Sep, 12AM (local time) - 4.5ft (1.3m), 7s period, ENE swell with offshore winds.
  • Most powerful swell: Thursday 10 Sep, 6PM (local time) - 5ft (1.6m), 7s period, ENE swell with 258 kJ wave energy.
  • Next surfable swell (1★+): Friday 11 Sep, 12AM (local time) - 4.5ft (1.3m), 7s period with ENE 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 (Sep 11) at 12AM. The primary swell is predicted to be 1.3m and 7s period with a secondary swell of 0.7m and 8s. Another secondary swell of 0.4m and 14s 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 1.6m 7s and forecast to arrive on Thursday (Sep 10) at 6PM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.1m 5s period and expected on Thursday (Sep 17) at 9AM.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+)12AM (Fri 11th Sep)4.5ft (1.3m) 7s
Best Surf12AM (Fri 11th Sep)4.5ft (1.3m) 7s
Most Powerful 6PM (Thu 10th Sep)5ft (1.6m) 7s

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


The Lowdown

Alright, listen up. Rusty here. We’ve got a strange one on our hands for the next couple of weeks. It’s not going to be a total flat spell, but it’s going to take a while before we see anything that’s really worth getting excited about. The ocean’s going to be out of sorts for a good stretch, so let’s just get through it and wait for that late burst of energy.

The first week is a write-off, plain and simple. Onjuku is going to see some small, weak swell, and the wind is just going to be messing with it. We're looking at days of poor surf and marginal conditions, with that S-SE swell struggling to show any power. There are a few mornings with cleaner conditions, but the swell is just too small to break properly. You'll see energy readings mostly in the low-to-mid hundreds, which tells you just how weak it all is.

It's not until Wednesday the 16th that we get a slight glimmer of hope. The wind goes light and offshore, and while the swell is still small at about 3 feet or less, it's clean and organized enough that it could be surfable for the patient types. It's a “good conditions” call, but we're talking knee-to-waist high at best. Not exactly firing.

Then on Friday the 18th, the swell starts to kick up a little bit more, with that period stretching out to 17 seconds. That’s a proper groundswell. But it’s still building, and the wind is a bit onshore at times, so it's going to be a bit lumpy. The energy jumps to over 1700, which is a huge leap from the weak stuff we had before, but the quality isn’t quite there yet.

Hold onto your boards, because Saturday the 19th is when things get serious. That long-period SE groundswell is going to be pouring in. We're looking at 13-foot faces at Onjuku. And here's the kicker: the wind is favorable and it's clean. But I gotta be straight with you, this is way too big for this break. 13 feet anywhere is a lot of water, but at a place like this, it's going to be a washing machine. The combined energy reading is over 8700, which is very strong, but this is a case of too much of a good thing. This is expert-only territory, and even then, it could be a complete closeout. This is a case where the setup looks far more interesting for the kite surfers than for us paddling.

The energy just builds from there. Sunday the 20th is still massive and untidy, with a 35-foot reading, and by Monday the 21st we hit the peak. We’re talking 32-foot faces with glassy conditions. That’s a monstrous, frightening swell. The energy reading is over 54,000, which is just off the charts. It's not surfable; it's a survival mission. The swell direction is also turning more southerly, which is cross-shore at Onjuku, making it a chaotic mess. After that peak, it backs off quickly.

By Tuesday the 22nd, it's dropping fast, but it's still got a lot of juice with 8-foot faces and lumpy conditions. The following days see it fade back into the small and messy stuff, with onshore winds and poor conditions through to the end of the month. The energy drops back to the low hundreds, and it’s nothing but closeouts and whitecaps.

So, there it is. A long spell of nothing much, a brief tease of clean but small surf, and then a monster swell that will be completely out of control and only for the most insane (or foolish) out there. It’s a weird forecast, for sure, but that’s the ocean for you. Just keep an eye on the charts; these long-range things can shift around a lot.

Stay safe out there.

Rusty.

Short Range Forecast

Moderate rain (total 12mm), heaviest on Thu morning. Warm (max 24°C on Fri morning, min 20°C on Thu morning). Winds decreasing (fresh winds from the NNE on Thu morning, light winds from the E by Fri morning).

Days 4-6 Weather Summary

Light rain (total 7mm), mostly falling on Sun night. Warm (max 27°C on Mon morning, min 23°C on Sun morning). Wind will be generally light.

Thursday
10
Friday
11
Saturday
12
Sunday
13
Monday
14
Tuesday
15
Wednesday
16
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
0
2
1
1
1
0
1
2
2
1
0
0
0
0
1
1
0
2
1
0
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
1.6
NE
7
1.5
ENE
7
1.3
ENE
7
0.5
E
14
0.5
E
14
0.6
E
14
0.6
E
14
0.6
E
13
0.6
E
13
0.7
ESE
13
0.8
ESE
13
0.8
SE
9
1.1
SE
9
1.2
SE
9
1.2
SE
9
0.7
E
14
0.7
E
14
0.7
E
13
0.7
E
13
0.7
E
12
0.6
E
12
Wave Graph
Metric surfscale
Energy kJ
230
223
162
106
101
136
134
128
128
176
225
108
188
230
220
201
203
180
165
145
102
Wind (km/h)
30
NNE
25
NE
20
NNE
10
NE
20
N
15
NNE
20
NNE
15
NNE
15
NNE
10
NNE
10
ESE
10
S
10
S
20
S
20
SSW
10
SW
10
S
15
SW
15
NE
20
NE
15
NE
Wind State
cross-off
cross-off
off
cross-off
off
cross-off
cross-off
cross-off
off
cross-off
cross-on
on
on
on
on
cross-on
on
cross-on
cross-off
cross-off
cross-off
High Tide
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
6:45AM1.29m
6:03PM1.43m
7:26AM1.19m
6:22PM1.41m
Low Tide
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
12:11PM0.69m
00:53AM0.27m
12:28PM0.79m
1:31AM0.32m
light rain
cloud
cloud
cloud
light rain
light rain
cloud
part cloud
part cloud
part cloud
clear
thunderstorm
thunderstorm
part cloud
cloud
cloud
thunderstorm
thunderstorm
cloud
light rain
light rain
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
5:16
5:16
5:18
5:18
5:18
5:20
5:20
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
5:53
5:52
5:51
5:49
5:47
5:46
5:45
 mm
4
4
4
2
1
1
3
1
2
Temp °C
21
22
21
24
21
21
21
23
23
25
25
26
27
27
26
26
26
26
24
24
24
Feels °C
19
21
20
27
21
21
21
25
25
28
29
30
30
29
28
30
29
29
27
25
26
  • Map Icons:
  • Break
  • Live Wave Height (m)
  • Live Wind Speed (km/h)
  • Surf Rating (10 Max)
  • Ocean Swells (m)
  • Wind Speed (km/h)
Map placeholder
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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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