Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 8 am 13 Aug 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
26.6° C
0.2° 

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


Onjuku surf forecast from 13 Aug 2026:

  • Best quality surf: Friday 14 Aug, 6AM (local time) - 5ft (1.6m), 10s period, E swell with cross-offshore winds.
  • Most powerful swell: Monday 17 Aug, 12AM (local time) - 7ft (2.1m), 10s period, E swell with 951 kJ wave energy.
  • Next surfable swell (1★+): Friday 14 Aug, 6AM (local time) - 5ft (1.6m), 10s 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 Friday (Aug 14) at 6AM. The primary swell is predicted to be 1.6m and 10s period with a secondary swell of 0.5m and 9s. The wind is predicted to be cross-offshore as the swell arrives.

The most powerful waves expected at Onjuku in the next 16 days are 2.1m 10s and forecast to arrive on Monday (Aug 17) at 12AM. Winds are predicted to be cross-offshore at the time the swell arrives.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+) 6AM (Fri 14th Aug)5ft (1.6m) 10s
Best Surf 6AM (Fri 14th Aug)5ft (1.6m) 10s
Most Powerful12AM (Mon 17th Aug)7ft (2.1m) 10s

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


The Lowdown

Alright, Rusty here. Let’s have a look at what’s on the cards for Onjuku over the next couple of weeks.

To be honest, the first week and a bit is a mixed bag. There are some waves around, but the conditions are often messy with that easterly swell and onshore or cross-off winds. The water temp is sitting at about 80°, which is bang average for this time of year – nothing unusual there. The real standout, the one worth circling on your calendar, is right at the tail end of the period, around the 23rd and 24th of August.

Let’s break it down. Thursday the 13th and Friday the 14th have some clean morning windows with chest-high swell around 5 to 5ft from the east, with a period of 9-10 seconds giving it moderate energy (in the 450-580 range). The wind is cross-offshore, so those morning sessions will be clean. Saturday the 15th sees the swell nudge up a touch to 6ft, but the wind picks up to a moderate breeze, making the surface a bit lumpy. Sunday the 16th and Monday the 17th have the best looking surf in this first stretch – Sunday morning is 6ft from the east with a cross-off north-easterly, and Monday morning bumps up to a clean 7ft from the east, period at 11 seconds giving it good energy (952). The wind is light and offshore, so you’ll get some nice clean lines. Onjuku is inconsistent though, so you’ll need to wait for the sets.

Then it goes quiet. From Tuesday the 18th through to Saturday the 22nd, the swell drops off a cliff – we’re talking knee-high to waist-high dribble, with onshore winds. That’s a solid 5-day gap of poor to flat conditions.

Now for the good stuff. On Sunday the 23rd of August, the afternoon session lights up. A solid 6ft swell from the southeast with a period of 14 seconds (very long groundswell) and the wind goes glassy – light air from the SSE. The energy jumps to 1822, so there is some serious push in the water. This is going to create some beautiful, clean, powerful waves. This is a day for experienced surfers – that 6ft is solid and the long period means it will be stacking up nicely on the banks. Monday the 24th of August morning is the absolute pick though. The swell holds at 8ft from the southeast, period stretching to 15 seconds, and the wind is glassy again. The combined energy is a massive 3288 – you are looking at some very strong, powerful surf from a true groundswell. This is expert territory, but the conditions will be pristine. After that, Tuesday the 25th gets too big – 13ft is just too much for this break, and it becomes dangerous. The rest of the week after that drops back down, with the swell fading and the winds turning onshore again.

So, if you want the best Onjuku has to offer, keep an eye on Sunday afternoon the 23rd and Monday morning the 24th of August. That’s your window for glassy, powerful groundswell. Just remember, it’s an inconsistent spot, so pick your moment.

Rusty.

Short Range Forecast

Heavy rain (total 30mm), heaviest during Thu night. Warm (max 28°C on Thu morning, min 24°C on Sat night). Wind will be generally light.

Days 4-6 Weather Summary

Mostly dry. Warm (max 27°C on Tue morning, min 22°C on Sun night). Wind will be generally light.

Thursday
13
Friday
14
Saturday
15
Sunday
16
Monday
17
Tuesday
18
Wednesday
19
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
2
2
2
3
2
1
2
1
2
3
2
3
3
2
1
1
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)
1.5
E
9
1.6
E
10
1.6
E
10
1.6
E
10
1.5
E
10
1.6
E
10
1.7
E
10
1.6
ESE
9
1.4
E
10
1.8
E
9
2
E
10
2.1
E
10
2
E
11
1.8
E
10
1.5
E
10
1.2
E
9
1
E
9
1
E
9
0.8
ENE
9
0.7
ENE
8
0.7
S
9
Wave Graph
Metric surfscale
Energy kJ
383
474
500
520
449
469
535
400
379
533
767
951
918
650
408
230
151
180
101
72
81
Wind (km/h)
15
ENE
15
E
15
E
15
ENE
15
E
20
ESE
20
E
20
ENE
15
NE
25
NE
20
ENE
15
NNE
15
NE
15
E
5
SSE
10
S
20
S
10
SSW
10
SW
20
SSW
10
SW
Wind State
cross-off
cross
cross
cross-off
cross
cross
cross
cross-off
cross-off
cross-off
cross-off
cross-off
cross-off
cross
cross-on
on
on
on
cross-on
cross-on
cross-on
High Tide
5:43PM1.38m
4:40AM1.50m
6:04PM1.38m
5:27AM1.47m
6:24PM1.39m
6:12AM1.40m
6:43PM1.39m
6:57AM1.29m
7:02PM1.40m
7:43AM1.18m
7:22PM1.39m
8:37AM1.06m
7:42PM1.36m
Low Tide
10:54AM0.03m
11:01PM0.75m
11:29AM0.11m
11:38PM0.63m
12:00PM0.24m
00:15AM0.53m
12:27PM0.38m
00:54AM0.46m
12:51PM0.53m
1:34AM0.43m
1:11PM0.67m
2:17AM0.43m
1:24PM0.80m
thunderstorm
thunderstorm
thunderstorm
thunderstorm
thunderstorm
thunderstorm
thunderstorm
clear
clear
clear
clear
clear
part cloud
part cloud
part cloud
part cloud
clear
clear
part cloud
clear
clear
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
4:56
4:56
4:56
4:58
4:58
4:58
5:00
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
6:30
6:29
6:28
6:27
6:25
6:23
6:22
 mm
1
2
13
1
2
10
1
Temp °C
28
27
26
27
27
25
27
27
24
26
26
24
26
26
25
27
27
26
29
29
27
Feels °C
30
29
29
29
30
27
26
26
25
25
25
25
27
28
28
29
28
29
31
31
31
  • 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
How to use the Wavefinder 
submit an eyeball surf report

Quick surf report for Onjuku:

join our community of surf reporters

FREE! Surf-Forecast.com widget for your website

The surf report / weather widget below is available to embed on third party websites free of charge and provides a summary of our Onjuku surf forecast. Simply grab the html code snippet that we provide and paste it into your own site. You can choose your preferred language and metric/imperial units for the surf forecast feed to suit users of your site. Click here to get the code.


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.

Nearest locationNearest