Nagaoka weather in September

In September, Nagaoka sees average daytime highs of 27°C and overnight lows near 19°C, with 144 mm of rain across 14 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 29°C in the first days to 24°C by the end. The sky is clear or mostly clear about 21% 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 Nagaoka's 6th-clearest and 9th-windiest month. For the whole year in context, see Nagaoka's year-round climate.

Daytime high
27°
3rd warmest
Overnight low
19°
10th coldest
Rainfall
144 mm
14 wet days
Daylight
12 h 12 min
5:32 AM – 5:46 PM
Cloud cover
66%
6th clearest
Wind
7 km/h
9th windiest
Solar energy
4.02 kWh/m²
Travel score
5.6
out of 10

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 24°C by the end.

A typical September day in Nagaoka 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 22°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)
12921
22921
32921
42921
52921
62821
72821
82820
92820
102820
112820
122720
132719
142719
152719
162619
172618
182618
192618
202618
212518
222517
232517
242517
252517
262416
272416
282416
292416
302416

How September really feels in Nagaoka

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.

Nagaoka weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -0°1792518.29.70.1
Feb / -0°12620.514.610.60.3
Mar10° / 12619.67.611.71.8
Apr16° / 9414.30.812.94.6
May22° / 12°9411.90146.3
Jun26° / 17°11512.5014.56.1
Jul29° / 22°20716.1014.34.6
Aug31° / 23°14614.1013.44.1
Sep27° / 19°14414012.35.6
Oct20° / 12°14314.80115.7
Nov14° / 14518.20.6103.3
Dec / 18123.7109.50.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 21% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 19% of September, with mostly cloudy or overcast conditions the remaining 60%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14456
24555
34456
44456
54456
64555
74456
84456
94456
104456
114357
124357
134258
144357
154159
164159
174060
183961
193862
203961
213862
223763
233763
243664
253664
263664
273664
283664
293664
303763

Chance of precipitation in September

Any precipitation

Nagaoka gets around 144 mm of rain over 14 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 48% and peaks near 50% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
149
250
350
450
550
650
750
850
950
1049
1149
1249
1348
1448
1547
1647
1747
1846
1946
2046
2146
2245
2345
2446
2546
2646
2747
2847
2947
3047

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 31% of days. Sticky, muggy-or-worse air turns up on roughly 48% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1021443382
2021544362
3031744352
4031844332
5041944322
6042044311
7052243291
8162343271
9172442251
10182541241
11292640221
122102839201
133112938191
143133036171
154143135160
165153233140
176173332120
188183330110
19919342890
201021342780
211222352560
221324352350
231425352150
241626351940
251728341830
261829341630
272030341420
282131331320
292332321110
302433311010

Wind in September

Winds average 7 km/h in September.

Across September, daily wind ranges from about 7 km/h on the calmest days to 8 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
218calm
228calm
238calm
248calm
258calm
268calm
278calm
288calm
298calm
308calm

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 6:10 PM to 5:24 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:196:10
212.85:206:08
312.85:216:07
412.75:226:05
512.75:226:03
612.65:236:02
712.65:246:00
812.65:255:59
912.55:265:57
1012.55:275:56
1112.45:285:54
1212.45:285:52
1312.45:295:51
1412.35:305:49
1512.35:315:48
1612.25:325:46
1712.25:335:44
1812.25:345:43
1912.15:345:41
2012.15:355:40
2112.05:365:38
2212.05:375:36
2311.95:385:35
2411.95:395:33
2511.95:405:32
2611.85:415:30
2711.85:415:28
2811.75:425:27
2911.75:435:25
3011.75:445:24

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.02 kWh/m².

For context, solar energy here swings from a low near 1.74 kWh/m² to a high of 5.68 kWh/m² in May across the year — September's 4.02 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.6Bright
24.5Bright
34.5Bright
44.4Bright
54.4Bright
64.3Bright
74.3Bright
84.3Bright
94.2Bright
104.2Bright
114.1Bright
124.1Bright
134.1Bright
144.0Bright
154.0Moderate
164.0Moderate
173.9Moderate
183.9Moderate
193.9Moderate
203.8Moderate
213.8Moderate
223.8Moderate
233.8Moderate
243.7Moderate
253.7Moderate
263.7Moderate
273.6Moderate
283.6Moderate
293.6Moderate
303.5Moderate
Planning a trip in September

Hazard calendar for Nagaoka

In seasonPeak

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

Nagaoka 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 Nagaoka?

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

5.6
Sightseeing
4th-best month of the year
5.7
Beach & pool
4th-best month of the year

September is a reasonable time to visit Nagaoka for sightseeing.

What to pack for Nagaoka in September

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

In September, Nagaoka sees daytime highs around 27°C and nights near 19°C. Pack rain gear. Worth having: light clothes. About 14 days see rain.

rain gearlight clothes

Sea temperature near Nagaoka 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 22 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 Nagaoka 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 Nagaoka peaks around August 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateAug 12UV 10Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun8Very high
Jul9Very high
Aug10Very high
Sep8Very high
Oct5High
Nov3Moderate
Dec2Low

Air quality in Nagaoka 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 Nagaoka 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 Nagaoka?

Nagaoka sits at 37.5°N, 138.8°E, 23 m above sea level, in Japan. The nearest listed city is Mitsuke, 12 km away.

Topography around Nagaoka

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

Within 3 km, the terrain around Nagaoka has only modest variations in elevation — a maximum elevation change of 53 m around an average of 23 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 741 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,314 m.

The land around Nagaoka is covered by artificial surfaces (64%) within 3 km, trees (59%) and cropland (25%) within 16 km, and trees (56%) and water (32%) within 80 km.

3 km
53 m
16 km
741 m
80 km
2,314 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Mitsuke 12 km · Tochio-honchō 13 km · Ojiya 17 km · Sanjō 21 km · Tsubame 25 km · Uonuma 25 km · Yoshida-kasugachō 26 km · Kashiwazaki 28 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 Nagaoka (37.45°, 138.85°, elevation 23 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).