Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 8 pm 10 Aug 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
27.4° C
0.7° 

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


Onjuku surf forecast from 10 Aug 2026:

  • Best quality surf: Tuesday 11 Aug, 6AM (local time) - 7.5ft (2.3m), 10s period, ENE swell with offshore winds.
  • Most powerful swell: Tuesday 11 Aug, 6PM (local time) - 8ft (2.4m), 12s period, ENE swell with 1,590 kJ wave energy.
  • Next surfable swell (1★+): Tuesday 11 Aug, 6AM (local time) - 7.5ft (2.3m), 10s 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 Tuesday (Aug 11) at 6AM. The primary swell is predicted to be 2.5m and 9s period with a secondary swell of 2.3m and 10s. Another secondary swell of 0.5m and 10s 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 2.4m 12s and forecast to arrive on Tuesday (Aug 11) 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 0.5m 4s period and expected on Tuesday (Aug 11) at 9AM.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+) 6AM (Tue 11th Aug)7.5ft (2.3m) 10s
Best Surf 6AM (Tue 11th Aug)7.5ft (2.3m) 10s
Most Powerful 6PM (Tue 11th Aug)8ft (2.4m) 12s

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


The Lowdown

Alright folks, Rusty here. Let’s get into it for Onjuku. We’ve got a bit of a wild ride ahead, but you gotta be patient.

The next 16 days start off with a bang, but it’s not for everyone. The first real surf kicks in on Monday, August 10th, with a solid 8ft easterly swell rolling in. The energy is cranking (1631), and the water is a warm 81°, which is about average for this time of year. However, the wind is a fresh cross-offshore from the NE at 22 mph, which keeps it clean, but those conditions are a little tricky. The swell period is 11 seconds, so it’s got some decent power, but for a beach break, that long period can make it a bit straight. This is expert territory at 8ft; definitely too big for beginners.

The standout window is Tuesday morning, August 11th. We’ve got a 7ft easterly swell with a 11-second period, and the wind is a clean offshore from the north at 12 mph. The energy is massive (1983), and the report says excellent surf for experienced surfers. This is the best on offer. The water temp is still warm, and the offshore wind will make those waves glassy. Crowds are a possibility here, so get out early.

Wednesday morning, August 12th, the swell drops right off to 4ft, and the wind goes cross-onshore, turning it into a bit of a mess. The energy plummets to 348. That’s no good.

Thursday, August 13th, through to Saturday, August 15th, is a bit of a mixed bag. Swell hangs around 5ft to 6ft, with mostly cross-offshore winds, but the energy is moderate. The wave comments are “marginal” or “questionable,” so it’s not really worth a special trip. The wind is moderate, and the swell is from the east-southeast, but the period is short (9-10 seconds), so the waves will be a bit crumbly.

Now, hold on to your board. Sunday, August 16th, we get another big pulse. The morning shows a 8ft easterly swell with a 10-second period, and the wind is a fresh offshore from the north at 22 mph. The energy is huge again (2092). This is a serious session, but it’s only for experts. The afternoon gets a bit messier with a strong offshore breeze at 25 mph, making it hard to paddle into. Monday, August 17th, continues with similar size and offshore winds, so if you’re an advanced surfer, that stretch from Sunday to Monday is your window.

After that, the bottom falls out. From Tuesday, August 18th, all the way through to Tuesday, August 25th, it’s a flat spell. The swell drops to under 3ft, the wind goes onshore or cross-onshore, and the energy is weak (under 300). The wave comments are all “poor” or “marginal.” It’s a solid week of nothing. The only small bright spot is a little 3ft pulse on the 22nd from the ESE, but with onshore wind, it’s not worth paddling out for.

So, to sum it up: the best surf is the morning of Tuesday, August 11th, and then the big, powerful, expert-only window from Sunday, August 16th, to Monday, August 17th. After that, put the board away for a week.

Rusty.

Short Range Forecast

Heavy rain (total 86mm), heaviest during Tue night. Warm (max 27°C on Thu morning, min 20°C on Tue night). Winds decreasing (fresh winds from the SW on Tue afternoon, light winds from the N by Wed night).

Days 5-7 Weather Summary

Heavy rain (total 37mm), heaviest during Sun afternoon. Warm (max 27°C on Fri morning, min 21°C on Sat night). Mainly fresh winds.

Tuesday
11
Wednesday
12
Thursday
13
Friday
14
Saturday
15
Sunday
16
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
3
3
0
0
1
2
2
2
1
3
2
1
2
2
1
2
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)
2.4
ENE
10
2.1
E
10
2.1
E
12
1.4
E
11
1.2
E
9
1.1
E
9
1.3
E
9
1.5
E
9
1.5
E
10
1.6
E
10
1.5
E
10
1.4
E
10
1.4
E
9
1.6
E
10
1.9
ESE
10
1.7
ESE
10
1.7
E
10
2
E
10
1.6
E
9
Wave Graph
Metric surfscale
Energy kJ
1023
969
1277
466
249
205
274
375
443
484
426
369
340
509
710
563
524
745
449
Wind (km/h)
30
NNE
20
NW
35
SW
35
SSE
10
E
15
NE
10
N
15
NE
15
ENE
15
N
25
NNE
20
NE
15
NNE
20
NE
30
NNE
30
NNE
25
NW
20
WSW
20
SW
Wind State
off
cross-off
cross-on
on
cross
cross-off
off
cross-off
cross-off
off
cross-off
cross-off
cross-off
cross-off
cross-off
off
cross-off
cross-on
cross-on
High Tide
1:48AM1.37m
4:57PM1.35m
2:54AM1.44m
5:21PM1.37m
3:50AM1.49m
5:43PM1.38m
4:40AM1.50m
6:04PM1.38m
5:27AM1.47m
6:24PM1.39m
6:12AM1.40m
6:43PM1.39m
Low Tide
9:31AM0.04m
9:44PM0.99m
10:15AM0.00m
10:23PM0.88m
10:54AM0.03m
11:01PM0.75m
11:29AM0.11m
11:38PM0.63m
12:00PM0.24m
00:15AM0.53m
12:27PM0.38m
00:54AM0.46m
part cloud
cloud
heavy rain
heavy rain
light rain
thunderstorm
part cloud
thunderstorm
clear
thunderstorm
thunderstorm
thunderstorm
thunderstorm
thunderstorm
part cloud
cloud
mod rain
heavy rain
thunderstorm
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
4:54
4:54
4:56
4:56
4:56
4:58
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
6:32
6:31
6:30
6:30
6:29
6:28
6:27
 mm
25
53
5
1
2
1
1
2
8
4
9
12
13
Temp °C
23
25
23
23
25
26
24
27
27
25
27
27
26
26
26
24
21
24
26
Feels °C
20
24
21
24
26
27
26
28
28
27
28
28
28
25
24
22
20
24
27
  • Map Icons:
  • Break
  • 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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