Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 2 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 12 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: Sunday 16 Aug, 9PM (local time) - 6.5ft (2.0m), 10s period, ESE swell with 742 kJ wave energy.
  • Next surfable swell (1★+): Thursday 13 Aug, 9AM (local time) - 5ft (1.5m), 9s 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 Thursday (Aug 13) at 9AM. The primary swell is predicted to be 1.5m and 9s period with a secondary swell of 0.6m and 10s. 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 2.0m 10s and forecast to arrive on Sunday (Aug 16) at 9PM. 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+) 9AM (Thu 13th Aug)5ft (1.5m) 9s
Best Surf 6AM (Fri 14th Aug)5ft (1.6m) 10s
Most Powerful 9PM (Sun 16th Aug)6.5ft (2.0m) 10s

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


The Lowdown

Alright, grab your board. This is Rusty, looking at the Onjuku stretch.

Right off the bat, for the next few days, Onjuku is going to be a bit of a tease. We've got surfable waves, but nothing that's going to have you calling in sick. The water temp is sitting at a normal 80°, nothing wild there. The swell is pretty weak, with combined energy readings mostly in the 200s and 500s (weak to moderate), so it's going to be a grovel-fest for the most part. The wind is a bit of a mixed bag too, with a fair amount of cross-off and cross conditions. Thursday the 13th is looking clean, but that energy is just not there. Don't get too excited for the weekend either, the energy picks up a touch but the wind turns more cross, making things a bit lumpy.

Things get quieter and weaker going into the middle of next week, with the swell dropping out and energy readings falling below 250. It’s not looking great, to be honest. There's a bit of a flat spell from around the 18th to the 23rd where I’d be finding something else to do, maybe fixing your dings. The swell energy is really weak, some days dropping to triple digits (like 103 and 62), and the wave heights are down around 1ft to 3ft. It’s a proper lull.

Now, here's where it gets interesting. There’s a promising pulse on Monday the 24th. The wind goes offshore early, and then in the afternoon, it’s glassy, absolutely clean. The swell comes back up around 4ft from the SE with a long 12-second period, and the energy jumps to 640 (moderate). This is the first real standout of the window.

But the real good stuff, the one we've been waiting for, is that big arrival on the 26th. That Wednesday morning is the one. We’re looking at a solid 7ft of SE swell with that same long 12-second period, and it's glassy. The energy is strong at 1452. This is going to be the pick of the whole stretch, and it’s the best wave you’ll find in the next couple of weeks. Just know that this size will be pushing it for anyone who isn’t comfortable on a bigger day.

After that, it gets big, but it gets messy. By the 27th, we’re talking about 13ft to 15ft of swell from the SE with 14-second periods. Power wise, we’re looking at strong to very strong energy readings of 6514 and 7885. But, this is way too much juice for Onjuku. It’s going to be a washing machine, not a surf spot. The wind is forecast to be on it, and conditions will be poor. Then by the 28th, the wind is howling onshore, and it’s blown out. That big swell is just going to be a messy, dangerous close-out. Unless you’re a masochist with a jet ski, give it a miss.

So, to sum it up: the 24th afternoon is a nice warm-up. The standout has to be the morning of the 26th – that’s the one to circle on the calendar. The swell direction is SSE which is good for this spot, it has size, period, and clean glass. After that, it’s just too much of a good thing.

Rusty, out.

Short Range Forecast

Heavy rain (total 37mm), heaviest during Thu night. Warm (max 27°C on Thu morning, min 23°C on Sat night). Wind will be generally light.

Days 4-6 Weather Summary

Mostly dry. Warm (max 27°C on Tue morning, min 23°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
1
1
2
2
3
2
3
3
3
1
0
0
0
1
2
1
2
Swell
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Height Map
Wave
Height (m)
Direction
Period (s)
1.5
E
9
1.6
E
10
1.6
E
10
1.6
E
10
1.5
E
10
1.7
E
10
1.7
E
10
1.6
ESE
10
1.4
E
10
1.6
E
8
1.8
E
9
1.9
ESE
10
1.7
E
10
1.6
E
10
1.3
E
9
1.2
E
9
1
E
8
0.9
ENE
8
0.9
SSE
8
1
SSE
9
1
SSE
9
Wave Graph
Metric surfscale
Energy kJ
383
480
500
520
450
527
535
502
379
347
565
671
550
470
274
225
140
118
120
166
166
Wind (km/h)
15
ENE
15
E
15
E
10
NE
15
E
20
ESE
20
E
20
ENE
15
NE
20
NE
25
ENE
10
NNE
15
NE
15
SE
10
SE
10
SE
15
ESE
10
E
15
NE
15
E
5
E
Wind State
cross-off
cross
cross
cross-off
cross
cross
cross
cross-off
cross-off
cross-off
cross-off
cross-off
cross-off
cross-on
cross-on
cross-on
cross-on
cross
cross-off
cross
glassy
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
rain showers
thunderstorm
thunderstorm
clear
rain showers
part cloud
part cloud
part cloud
part cloud
part cloud
part cloud
clear
clear
part cloud
part cloud
part cloud
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
2
2
18
4
1
7
2
1
Temp °C
27
27
26
27
27
25
27
27
25
26
26
23
26
26
25
27
27
25
27
27
25
Feels °C
29
29
29
29
28
27
27
27
26
26
25
24
28
28
27
29
29
27
30
30
29
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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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