Uonuma weather in September

In September, Uonuma sees average daytime highs of 24°C and overnight lows near 17°C, with 190 mm of rain across 16.6 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 27°C in the first days to 22°C by the end. The sky is clear or mostly clear about 17% of the time in September, and the air most often feels humid.

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 Uonuma's 6th-clearest and 9th-windiest month. For the whole year in context, see Uonuma's year-round climate.

Daytime high
24°
3rd warmest
Overnight low
17°
10th coldest
Rainfall
190 mm
16.6 wet days
Daylight
12 h 12 min
5:31 AM – 5:46 PM
Cloud cover
70%
6th clearest
Wind
6 km/h
9th windiest
Solar energy
3.87 kWh/m²
Travel score
5.5
out of 10

Uonuma is city in Niigata Prefecture, Japan.

Density
36/km²
people per km²
Founded
2004

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 27°C in the first days to 22°C by the end.

A typical September day in Uonuma reaches about 24°C in the afternoon and slips back to 17°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between 20°C and 29°C. Set against its neighbours, September runs about 4°C cooler than August and about 6°C warmer than October.

10°20°30°151015202530
Avg high (°C)Avg low (°C)
12719
22719
32719
42619
52619
62619
72618
82618
92618
102518
112518
122517
132517
142517
152417
162417
172416
182416
192416
202316
212315
222315
232315
242215
252215
262214
272214
282214
292214
302114

How September really feels in Uonuma

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.

Uonuma weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -3°29826.224.19.70.0
Feb / -3°2232219.810.60.0
Mar / -1°20121.614.811.70.6
Apr14° / 14316.43.612.93.4
May20° / 10°152150.1145.5
Jun23° / 15°17816.6014.55.5
Jul27° / 20°26320.5014.34.7
Aug28° / 21°18017.8013.44.9
Sep24° / 17°19016.6012.35.5
Oct18° / 10°19616.60114.9
Nov12° / 19218.83.9102.5
Dec / -2°2712417.69.50.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 17% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 66%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13862
23862
33862
43763
53763
63763
73664
83664
93763
103763
113664
123565
133664
143565
153466
163466
173466
183367
193268
203268
213169
223169
233169
243169
253070
263070
273070
282971
293070
303070

Chance of precipitation in September

Any precipitation

Uonuma gets around 190 mm of rain over 16.6 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 56% and peaks near 59% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
159
259
359
459
559
659
759
858
958
1058
1158
1257
1357
1456
1556
1655
1755
1854
1954
2054
2153
2253
2353
2453
2553
2654
2754
2854
2954
3054

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the humid band about 31% of days. Sticky, muggy-or-worse air turns up on roughly 33% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
106295015
216305013
317314912
418324811
518324711
629334610
721034449
831235438
931335417
1041435407
1151636386
1261736365
1371836345
1482035324
15102235304
16112335283
17132534253
18152634232
19172833212
20192932191
21213131171
22233230151
23253328131
24273427110
2529362690
2631372580
2732382360
2834392250
2936392040
3038401930

Wind in September

Winds average 6 km/h in September.

Across September, daily wind ranges from about 5 km/h on the calmest days to 6 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
296calm
306calm

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 5:19 AM to 5:44 AM, and sunset from 6:09 PM to 5:23 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:196:09
212.85:206:07
312.85:206:06
412.75:216:04
512.75:226:03
612.65:236:01
712.65:246:00
812.65:255:58
912.55:255:57
1012.55:265:55
1112.45:275:53
1212.45:285:52
1312.45:295:50
1412.35:305:49
1512.35:315:47
1612.25:315:46
1712.25:325:44
1812.25:335:42
1912.15:345:41
2012.15:355:39
2112.05:365:38
2212.05:375:36
2311.95:375:34
2411.95:385:33
2511.95:395:31
2611.85:405:30
2711.85:415:28
2811.75:425:26
2911.75:435:25
3011.75:445:23

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.87 kWh/m².

For context, solar energy here swings from a low near 1.87 kWh/m² to a high of 5.55 kWh/m² in May across the year — September's 3.87 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.4Bright
24.3Bright
34.3Bright
44.2Bright
54.2Bright
64.2Bright
74.1Bright
84.1Bright
94.0Bright
104.0Bright
114.0Moderate
123.9Moderate
133.9Moderate
143.9Moderate
153.8Moderate
163.8Moderate
173.8Moderate
183.8Moderate
193.7Moderate
203.7Moderate
213.7Moderate
223.6Moderate
233.6Moderate
243.6Moderate
253.5Moderate
263.5Moderate
273.5Moderate
283.5Moderate
293.4Moderate
303.4Moderate
Planning a trip in September

Hazard calendar for Uonuma

In seasonPeak

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

Uonuma 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 Uonuma?

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

5.5
Sightseeing
1st-best month of the year
4.6
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Uonuma for sightseeing.

What to pack for Uonuma in September

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

In September, Uonuma sees daytime highs around 24°C and nights near 17°C. Pack rain gear. Worth having: light clothes. About 17 days see rain.

rain gearlight clothes

Sea temperature near Uonuma in September

The nearest coast averages about 25°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 33 km away) is warmest in August at about 27°C and coldest in March near 10°C.

It's comfortable for a long swim from Jun 21 to Oct 31 — about 4.4 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan12Bracing
Feb11Bracing
Mar10Bracing
Apr11Bracing
May15Bracing
Jun20Cool
Jul23Refreshing
Aug27Warm
Sep25Warm
Oct22Refreshing
Nov18Cool
Dec15Cool

UV index in Uonuma in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Uonuma peaks around August 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 2 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateAug 12UV 10Dec 21UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar5Moderate
Apr7High
May8Very high
Jun9Very high
Jul10Very high
Aug10Very high
Sep8Very high
Oct5High
Nov3Moderate
Dec2Moderate

Air quality in Uonuma 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 Uonuma is worst in April — around 23 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodApr 1723 µg/m³Dec 1610 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb15Moderate
Mar22Moderate
Apr23Moderate
May22Moderate
Jun19Moderate
Jul17Moderate
Aug14Moderate
Sep12Moderate
Oct12Good
Nov11Good
Dec10Good
Location & terrain

Where is Uonuma?

Uonuma sits at 37.2°N, 139.0°E, 95 m above sea level, in Japan. The nearest listed city is Ojiya, 16 km away.

Topography around Uonuma

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

Within 3 km, the terrain around Uonuma has significant variations in elevation — a maximum elevation change of 251 m around an average of 138 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,713 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,554 m.

The land around Uonuma is covered by trees (43%), cropland (29%) and artificial surfaces (21%) within 3 km, trees (82%) within 16 km, and trees (70%) within 80 km.

3 km
251 m
16 km
1,713 m
80 km
2,554 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Ojiya 16 km · Minamiuonuma 20 km · Muikamachi 21 km · Tōkamachi 21 km · Nagaoka 25 km · Shiozawa 25 km · Tochio-honchō 26 km · Mitsuke 32 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 Uonuma (37.2449°, 138.9623°, elevation 95 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).