Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 8 am 08 Sep 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
28.0°C
1.5° 

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


Onjuku surf forecast from 8 Sep 2026:

  • Best quality surf: Thursday 10 Sep, 9AM (local time) - 5ft (1.6m), 7s period, NE swell with offshore winds.
  • Most powerful swell: Wednesday 9 Sep, 6PM (local time) - 8ft (2.5m), 9s period, SSW swell with 972 kJ wave energy.
  • Next surfable swell (1★+): Thursday 10 Sep, 9AM (local time) - 5ft (1.6m), 7s period with NE 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 Thursday (Sep 10) at 9AM. The primary swell is predicted to be 1.6m and 7s period with a secondary swell of 1.3m and 8s. Another secondary swell of 0.3m and 15s 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 2.5m 9s and forecast to arrive on Wednesday (Sep 09) at 6PM. 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 6s period and expected on Sunday (Sep 13) at 6AM.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+) 9AM (Thu 10th Sep)5ft (1.6m) 7s
Best Surf 9AM (Thu 10th Sep)5ft (1.6m) 7s
Most Powerful 6PM (Wed 9th Sep)8ft (2.5m) 9s

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


The Lowdown

Alright, grab your board and let’s look at what the ocean’s got cookin’ for the next couple of weeks.

The next week is going to be a bit of a grind. We've got a quiet, messy stretch ahead with not much to get excited about. We're looking at a real dry spell from now until about the middle of next week, where there's just nothing worth paddling out for. The wind's mostly onshore or cross, and the swell is small and junky. If you're jonesing, maybe just wait it out on the beach with a cold one.

Things start to perk up a bit around the 10th. Thursday morning (the 10th) shows a bit of life with a NE wind creating some clean, offshore conditions at Onjuku. The swell jumps to 5ft from the NE, but it's only a 7-second period, so it'll be a bit soft and crumbly. It's not epic, but it's a start. The energy reading is moderate at 525, which is better than the weak stuff we'll have seen. The water is a touch warmer than normal at 82°F, which is noticeable for this time of year.

The following morning, Friday the 11th, looks a little cleaner with lighter NE winds. Swell drops to 3ft from the ENE, and while the energy is weaker (337), it's rideable. There's a longer-period pulse of 14 seconds on Friday afternoon, but the swell is tiny at 2ft, so it's more of a promise than a reality.

Saturday and Sunday (the 12th and 13th) are similar. Small, clean-ish waves in the 2ft range from the east, with light winds. It's the kind of surf that's fun if you're a log-head or just want to get wet, but there's no push to it. The energy is hanging around the 200s, so it's pretty weak.

Now, Monday the 14th is where I start to raise an eyebrow. We've got a glassy morning with a bit more size, 4ft from the SE. The wind is almost nothing, just a slight air, and the period is a more workable 9 seconds. The energy is moderate at 344. It’ll be clean and might offer a fun wave or two.

Then we hit another lull in the middle of the week. The 15th, 16th, and 17th look pretty ordinary. The swell is small, and the wind gets fresh and blustery from the SW and NE. It's all poor conditions. The 18th gets stronger wind, and the 19th is just tiny leftovers.

But hold on to your hats, because that's when the ocean wakes up. It's a long way out, but the forecast for September 20th is looking like the standout of the entire period. This is the one to circle on your calendar. The swell is from the SE and building. The combined energy jumps to a strong 3260, and the swell height is 7ft with a very long 18-second period. That's a serious groundswell, and it's going to have some real push behind it. The wind is light and offshore from the NE, which will keep it clean. This is a call for experienced surfers though, as the power is on. This big, long-period swell can turn a beach break like Onjuku into a bit of a closeout machine, so I'd be looking for a reef or a point if you know the area.

The 20th is just the beginning. The 21st is looking, well, huge. We're talking 13ft from the SSE with a very long 18-second period. The energy readings are off the charts at 9530, but even that is understating it. The problem is, the wind is howling offshore at 28 mph, which will make it a battle just to get out. The forecast says it's predicted to be too big for this break, and I'd have to agree. It’s going to be a washing machine out there. This is only for the most fearless, experienced chargers, and even then, take a deep breath.

After that, it into Monday the 22nd still has big swell—12ft from the SE—and the energy is still massive at 9298. The wind looks a little better, but it's still too big and messy for Onjuku. Tuesday the 23rd is still oversized and the wind is back onshore. The size is still there but the quality is gone.

So there you have it. A quiet week, a rippable morning or two, and then one hell of a big swell event right at the end. The standout is the morning of Sunday, September 20th. It's far out, so treat it as promising but not set in stone. Forecasts can change, but that’s the one I’d have my eye on. Other than that, be patient.

Later,

Rusty

Short Range Forecast

Heavy rain (total 31mm), heaviest during Wed night. Warm (max 28°C on Tue morning, min 20°C on Wed night). Winds decreasing (strong winds from the SW on Tue night, light winds from the NNE by Thu night).

Days 4-6 Weather Summary

Some drizzle, heaviest during Sun night. Warm (max 26°C on Sun morning, min 21°C on Fri morning). Wind will be generally light.

Tuesday
8
Wednesday
9
Thursday
10
Friday
11
Saturday
12
Sunday
13
Monday
14
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
0
0
0
1
3
1
2
2
2
2
2
0
1
2
2
2
2
0
2
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
1.7
S
9
1.6
S
9
1.8
S
8
2.3
S
8
2.1
S
8
1.8
NE
7
1.6
NE
7
1.4
NE
7
1.2
ENE
8
1
ENE
8
0.9
S
8
0.6
E
14
0.6
E
14
0.6
E
13
0.6
E
13
0.6
E
13
0.9
SE
9
1
SE
9
1.1
SE
9
1.1
SE
9
1.1
SE
9
Wave Graph
Metric surfscale
Energy kJ
473
404
448
686
626
319
240
201
157
117
101
136
134
128
128
123
125
159
225
216
202
Wind (km/h)
15
SW
20
SSW
35
SSW
40
SW
35
SW
30
NNE
25
NNE
25
N
20
NNE
15
NNE
15
NNE
15
NE
15
NE
20
NE
10
NNE
10
NNE
15
E
5
ESE
5
ESE
15
SSE
5
SE
Wind State
cross-on
on
cross-on
cross-on
cross-on
cross-off
off
off
off
off
cross-off
cross-off
cross-off
cross-off
off
cross-off
cross-off
glassy
glassy
on
glassy
High Tide
3:57PM1.30m
2:06AM1.33m
4:14PM1.34m
3:06AM1.40m
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
Low Tide
8:59PM0.95m
9:17AM0.17m
9:34PM0.80m
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
part cloud
part cloud
thunderstorm
thunderstorm
thunderstorm
heavy rain
light rain
light rain
mod rain
cloud
cloud
cloud
cloud
part cloud
part cloud
part cloud
clear
thunderstorm
part cloud
clear
clear
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
5:15
5:16
5:16
5:16
5:18
5:18
5:18
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
5:57
5:54
5:53
5:52
5:51
5:49
5:47
 mm
7
1
2
13
1
1
6
1
Temp °C
28
28
27
28
28
23
21
20
21
21
22
22
23
23
22
26
26
25
27
26
25
Feels °C
30
30
28
27
28
23
20
18
19
22
24
24
25
24
24
29
29
29
30
28
29
  • 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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