Ōtsu weather in September

In September, Ōtsu sees average daytime highs of 27°C and overnight lows near 19°C, with 187 mm of rain across 12.9 wet days and about 12.2 hours of daylight. It is the 3rd-warmest and 3rd-wettest month of the year here.

Highs ease over the month, from about 29°C in the first days to 25°C by the end. The sky is clear or mostly clear about 28% of the time in September, and the air most often feels muggy.

Daylight stretches from about 12 h 48 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Ōtsu's 8th-clearest and 6th-windiest month. For the whole year in context, see Ōtsu's year-round climate.

Daytime high
27°
3rd warmest
Overnight low
19°
10th coldest
Rainfall
187 mm
12.9 wet days
Daylight
12 h 12 min
5:44 AM – 5:57 PM
Cloud cover
64%
8th clearest
Wind
9 km/h
6th windiest
Solar energy
4.09 kWh/m²
Travel score
5.8
out of 10

Ōtsu is city of Shiga Prefecture, Japan.

Density
744/km²
people per km²
Founded
1933

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 29°C in the first days to 25°C by the end.

A typical September day in Ōtsu reaches about 27°C in the afternoon and slips back to 19°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between 23°C and 31°C. Set against its neighbours, September runs about 4°C cooler than August and about 6°C warmer than October.

10°15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13022
23022
32922
42921
52921
62921
72921
82921
92821
102820
112820
122820
132820
142720
152720
162719
172719
182719
192619
202619
212618
222618
232618
242518
252518
262517
272517
282517
292417
302417

How September really feels in Ōtsu

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Ōtsu weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -0°647.92.39.91.1
Feb / 708.92.310.71.5
Mar12° / 12212.40.611.73.1
Apr18° / 13311.7012.95.4
May23° / 13°15311.6013.86.4
Jun26° / 18°20514.6014.35.6
Jul30° / 22°23917.6014.14.2
Aug31° / 23°14013.5013.34.1
Sep27° / 19°18712.9012.25.8
Oct21° / 13°1619.9011.16.6
Nov16° / 847.6010.25.1
Dec10° / 657.719.72.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 28% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 57%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14258
24258
34258
44258
54258
64258
74357
84357
94357
104357
114357
124456
134456
144456
154258
164357
174357
184258
194258
204258
214159
224258
234258
244258
254357
264357
274357
284357
294357
304456

Chance of precipitation in September

Any precipitation

Ōtsu gets around 187 mm of rain over 12.9 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 43% and peaks near 45% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
144
244
345
445
545
645
745
845
945
1045
1145
1245
1345
1444
1544
1643
1743
1842
1942
2041
2141
2241
2341
2440
2540
2640
2740
2840
2940
3040

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the muggy band about 28% of days. Sticky, muggy-or-worse air turns up on roughly 50% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1031536441
2031636431
3041736421
4041836411
5051935401
6152135381
7162234370
8162334350
9172533330
10182633320
11292732300
122102832280
133112931260
143123030240
154143130220
164153229200
175163228180
186183227170
197193326150
208213325130
219223224120
2210243223100
231125322290
241227322180
251328312070
261429311960
271630311850
281731301740
291832301640
302033291530

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 8 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
158calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 48 min at the start of September to 11 h 42 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over September. Sunrise moves from 5:33 AM to 5:55 AM, and sunset from 6:19 PM to 5:37 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:336:19
212.75:346:18
312.75:356:17
412.75:356:15
512.65:366:14
612.65:376:12
712.65:386:11
812.55:386:09
912.55:396:08
1012.45:406:06
1112.45:416:05
1212.45:416:03
1312.35:426:02
1412.35:436:00
1512.35:445:59
1612.25:445:57
1712.25:455:56
1812.15:465:54
1912.15:475:53
2012.15:475:51
2112.05:485:50
2212.05:495:48
2312.05:505:47
2411.95:505:45
2511.95:515:44
2611.85:525:42
2711.85:535:41
2811.85:545:39
2911.75:545:38
3011.75:555:37

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.09 kWh/m².

For context, solar energy here swings from a low near 2.25 kWh/m² to a high of 5.41 kWh/m² in May across the year — September's 4.09 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.6Bright
34.6Bright
44.5Bright
54.5Bright
64.4Bright
74.4Bright
84.3Bright
94.3Bright
104.3Bright
114.2Bright
124.2Bright
134.2Bright
144.1Bright
154.1Bright
164.1Bright
174.0Bright
184.0Bright
194.0Moderate
204.0Moderate
213.9Moderate
223.9Moderate
233.9Moderate
243.8Moderate
253.8Moderate
263.8Moderate
273.7Moderate
283.7Moderate
293.7Moderate
303.6Moderate
Planning a trip in September

Hazard calendar for Ōtsu

In seasonPeak

In September, Ōtsu sits inside its pacific typhoon season. The full year is below, with each hazard's peak months called out.

Ōtsu sits in the Pacific typhoon belt; the season peaks July–October.

Pacific typhoon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Ōtsu?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.8
Sightseeing
3rd-best month of the year
6.0
Beach & pool
1st-best month of the year

September is a reasonable time to visit Ōtsu for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Ōtsu in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Ōtsu sees daytime highs around 27°C and nights near 19°C. Pack light clothes. Worth having: rain gear. About 13 days see rain.

light clothesrain gear

Sea temperature near Ōtsu in September

The nearest coast averages about 26°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 61 km away) is warmest in August at about 27°C and coldest in February near 13°C.

It's comfortable for a long swim from Jun 6 to Nov 11 — about 5.2 months when the water holds above 20°C.

10°15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan14Bracing
Feb13Bracing
Mar13Bracing
Apr15Cool
May18Cool
Jun21Refreshing
Jul25Warm
Aug27Warm
Sep26Warm
Oct23Refreshing
Nov20Cool
Dec17Cool

UV index in Ōtsu in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 9 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Ōtsu peaks around June 23 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJun 23UV 10Dec 23UV 3
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5High
Apr7High
May8Very high
Jun10Very high
Jul10Very high
Aug9Very high
Sep9Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Ōtsu in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Ōtsu is worst in April — around 24 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (October, 12 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateApr 1723 µg/m³Oct 1812 µg/m³
PM2.5 (µg/m³)Level
Jan14Moderate
Feb17Moderate
Mar22Moderate
Apr24Moderate
May22Moderate
Jun19Moderate
Jul17Moderate
Aug17Moderate
Sep14Moderate
Oct12Good
Nov13Moderate
Dec12Moderate
Location & terrain

Where is Ōtsu?

Ōtsu sits at 35.0°N, 135.9°E, 131 m above sea level, in Japan. The nearest listed city is Kusatsu, 9.0 km away.

Topography around Ōtsu

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Ōtsu.

Within 3 km, the terrain around Ōtsu has significant variations in elevation — a maximum elevation change of 502 m around an average of 176 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 840 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,423 m.

The land around Ōtsu is covered by trees (46%), artificial surfaces (30%) and water (22%) within 3 km, trees (48%) and artificial surfaces (34%) within 16 km, and trees (62%) within 80 km.

3 km
502 m
16 km
840 m
80 km
1,423 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Kusatsu 9.0 km · Kamigyō-ku 11 km · Kyoto 11 km · Rittō 12 km · Moriyama 13 km · Uji 13 km · Mukō 15 km · Kōtari 17 km

Japan travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B
100 V · 50 / 60 Hz
Prices
≈ 65% of US
price level, 2025
GDP per capita
$35,951
2025
Happiness
6.1 / 10
World Happiness, 2025
Safe drinking water
99%
of population, 2024
Homicide rate
0.2
per 100k, 2023
Road deaths
3.6
per 100k/yr, 2019
Income group
High
World Bank
English
Very low
EF EPI 446
Religion
Shintoism 49%Buddhism 46%other 4%Christianity 1%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Ōtsu (35°, 135.8667°, elevation 131 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).