Onjuku Surf Break

Lat Long: 35.18° N 140.35° E

Onjuku Surf Forecast and Surf Report

Issued: 8 am 15 Aug 2026 (local time)

Forecast update in  hr  min

Today's Onjuku sea temperature is
26.8° C
0.0° 

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


Onjuku surf forecast from 15 Aug 2026:

  • Best quality surf: Sunday 16 Aug, 12AM (local time) - 4.5ft (1.3m), 9s period, ESE swell with cross-offshore winds.
  • Most powerful swell: Saturday 15 Aug, 9PM (local time) - 5ft (1.5m), 10s period, ESE swell with 391 kJ wave energy.
  • Next surfable swell (1★+): Sunday 16 Aug, 12AM (local time) - 4.5ft (1.3m), 9s period with ESE 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 Sunday (Aug 16) at 12AM. The primary swell is predicted to be 1.3m and 9s 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 1.5m 10s and forecast to arrive on Saturday (Aug 15) at 9PM. Winds are predicted to be cross-shore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.4m 3s period and expected on Wednesday (Aug 19) at 12PM.

Wave TypeTime (JST) & Date Wave Height & Period
Next good surf (1 star+)12AM (Sun 16th Aug)4.5ft (1.3m) 9s
Best Surf12AM (Sun 16th Aug)4.5ft (1.3m) 9s
Most Powerful 9PM (Sat 15th Aug)5ft (1.5m) 10s

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


The Lowdown

Alright folks, Rusty here, checkin' in with the local skinny. We're lookin' at a pretty quiet run for Onjuku for the next week or so, but the charts are hinting at something big and a little wild further out. Let's get into it.

The water temp is sittin' right on 80°, which is dead average for this time of year. No surprises there.

So, the first two weeks are a bit of a write-off for proper waves. The combined swell energy is low, mostly in the 150 to 650 range, but it does pop up to a moderate 632 on Sunday morning the 16th. Still, the wind is a constant cross-shore, making things messy and choppy. The swell is mostly from the E/ESE with short periods around 8-10 seconds, so it's weak, short-period windswell. It's not gonna be any good. We've got a few days where the wind eases to a light breeze and it cleans up, like Tuesday morning, the 18th, but the swell drops to 3 ft with a period of only 8 seconds. You might get a few knee-high peelers, but it's a struggle. Honestly, we're looking at a solid 10-day gap of poor to marginal surf.

Now, hold onto your board. The real story starts around Monday, the 24th of August. We see a massive jump in the numbers. The combined swell energy hits a whopping 4540 on Monday morning, with swell from the SE, 8 ft and a period of 17 seconds. That's very long-period groundswell, and it's packing serious power. The wind is a clean cross-offshore from the NE. This is the standout of the whole forecast. The water will be a mess, but the lines will be clean. It's a big swell, though, over 8 ft, so this is strictly for experienced surfers only. The long period is great for wrapping around points, but at a beach break like Onjuku, it might break a bit too straight in sections.

The standouts keep coming, but they get too big. Tuesday morning the 25th has 12 ft SSE swell with 15-second periods, and 5145 energy. The wind is still clean cross-off. Wednesday the 26th is even bigger, with 13 ft SSE swell. The combined energy hits 6071. By Thursday the 27th, it's a monster 15 ft SSE swell, with a staggering 10173 combined energy. The wind that morning is a cross-off, but it looks like the swell is predicted to be too big for this break. It's gonna be a washing machine. Thursday afternoon the wind swings to a strong onshore, and the whole thing just gets blown out.

So, the call is simple. Don't bother for the first week and a half. The standout is Monday, the 24th of August, with that 8 ft SE groundswell and clean, cross-off wind. It's big, it's powerful, and it's for the crew who know what they're doing. After that, it's either too big for Onjuku or blown out. The forecast is reliable for the near term, but that long-range call for the 24th is a solid bet.

Rusty, signing off.

Short Range Forecast

Light rain (total 4mm), mostly falling on Sun morning. Warm (max 27°C on Sat morning, min 24°C on Sat night). Wind will be generally light.

Days 4-6 Weather Summary

Some drizzle, heaviest during Thu morning. Warm (max 27°C on Tue morning, min 24°C on Tue night). Wind will be generally light.

Saturday
15
Sunday
16
Monday
17
Tuesday
18
Wednesday
19
Thursday
20
Friday
21
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
AM
PM
Night
Rating
(10 max)
1
0
2
1
0
1
1
0
0
2
0
1
0
0
1
0
0
0
1
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)
1.6
ESE
10
1.5
ESE
9
1.3
ESE
9
1.4
E
10
1.2
E
8
1.2
E
9
1.1
E
9
1
E
8
1
E
8
1
E
8
0.9
ESE
8
1
ESE
7
1
E
7
1
E
7
0.9
E
8
1.1
E
8
1.2
ESE
8
1.4
ESE
8
1.2
ESE
8
1.1
ESE
7
0.8
S
10
Wave Graph
Metric surfscale
Energy kJ
435
367
308
356
200
230
186
144
144
134
101
99
106
88
89
146
187
237
155
121
130
Wind (km/h)
15
E
20
E
15
ENE
15
E
20
E
15
E
15
E
15
ESE
10
E
10
ENE
15
E
10
ENE
15
NE
15
ENE
10
ENE
15
ENE
15
ESE
10
ESE
10
ESE
10
ESE
10
SSE
Wind State
cross
cross
cross-off
cross
cross
cross
cross
cross
cross
cross-off
cross
cross-off
cross-off
cross-off
cross-off
cross-off
cross
cross-on
cross
cross-on
cross-on
High Tide
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
9:58AM0.96m
8:05PM1.32m
8:35PM1.27m
Low Tide
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
3:09AM0.46m
1:21PM0.89m
4:20AM0.49m
clear
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rain showers
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rain showers
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clear
clear
clear
thunderstorm
part cloud
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rain showers
<span class="translation_missing" title="translation missing: en.weather_tables.sunrise">Sunrise</span>
4:56
4:58
4:58
4:58
5:00
5:01
5:01
<span class="translation_missing" title="translation missing: en.weather_tables.sunset">Sunset</span>
6:28
6:27
6:25
6:23
6:22
6:22
6:21
 mm
2
2
1
1
Temp °C
27
27
25
26
26
25
27
27
25
27
27
25
27
27
25
27
27
25
27
27
26
Feels °C
28
28
26
26
27
27
29
29
27
29
29
28
29
29
28
29
29
27
29
29
29
  • 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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