Ōmachi weather in September

In September, Ōmachi sees average daytime highs of 19°C and overnight lows near 12°C, with 292 mm of rain across 19.1 wet days and about 12.2 hours of daylight. It is the 3rd-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 21°C in the first days to 17°C by the end. The sky is clear or mostly clear about 11% of the time in September, and the air most often feels dry.

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 Ōmachi's 9th-clearest and 11th-windiest month. For the whole year in context, see Ōmachi's year-round climate.

Daytime high
19°
3rd warmest
Overnight low
12°
10th coldest
Rainfall
292 mm
19.1 wet days
Daylight
12 h 12 min
5:36 AM – 5:50 PM
Cloud cover
75%
9th clearest
Wind
5 km/h
11th windiest
Solar energy
3.98 kWh/m²
Travel score
4.6
out of 10

Ōmachi is dissolved municipality in Kitaazumi district, Nagano prefecture, Japan.

Founded
1889

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 21°C in the first days to 17°C by the end.

A typical September day in Ōmachi reaches about 19°C in the afternoon and slips back to 12°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 15°C and 23°C. Set against its neighbours, September runs about 4°C cooler than August and about 6°C warmer than October.

10°15°20°25°151015202530
Avg high (°C)Avg low (°C)
12215
22215
32114
42114
52114
62114
72114
82114
92114
102013
112013
122013
132013
142013
151912
161912
171912
181912
191911
201811
211811
221811
231810
241810
251710
261710
271710
28179
29179
30179

How September really feels in Ōmachi

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.

Ōmachi weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan-5° / -11°19322.4249.80.0
Feb-3° / -10°16718.319.610.60.0
Mar / -6°2111919.111.70.0
Apr / -1°20016.69.912.90.9
May14° / 23717.81.313.93.5
Jun18° / 11°34420.6014.44.1
Jul22° / 15°45124.4014.24.3
Aug23° / 16°29721.9013.44.9
Sep19° / 12°29219.1012.24.6
Oct13° / 22716.31.111.13.2
Nov / -2°18317.311.110.10.6
Dec-2° / -8°19621.421.49.60.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 11% 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 74%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
12575
22575
32575
42476
52476
62476
72575
82575
92575
102575
112674
122674
132674
142773
152674
162674
172674
182773
192773
202674
212674
222773
232773
242773
252773
262872
272971
282872
292872
302872

Chance of precipitation in September

Any precipitation

Ōmachi gets around 292 mm of rain over 19.1 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 64% and peaks near 72% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%151015202530
Rain chance (%)
172
272
372
472
571
670
770
869
968
1067
1166
1265
1364
1464
1563
1662
1762
1861
1961
2060
2160
2259
2359
2459
2559
2659
2759
2859
2959
3059

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 52% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
11940392
22141371
32241361
42441341
52641321
62842301
73042280
83242260
93441240
103641230
113940210
124140190
134439170
144638160
154936140
165235130
175533120
185832100
19613090
20642880
21672670
22692560
23712360
24742150
25771940
26791740
27811630
28831430
29851320
30861220

Wind in September

Winds average 5 km/h in September.

Across September, daily wind ranges from about 4 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
14calm
24calm
34calm
44calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

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 5:24 AM to 5:48 AM, and sunset from 6:13 PM to 5:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:246:13
212.85:256:11
312.75:256:10
412.75:266:08
512.75:276:07
612.65:286:05
712.65:296:04
812.55:296:02
912.55:306:01
1012.55:315:59
1112.45:325:58
1212.45:335:56
1312.35:345:54
1412.35:345:53
1512.35:355:51
1612.25:365:50
1712.25:375:48
1812.15:385:47
1912.15:385:45
2012.15:395:43
2112.05:405:42
2212.05:415:40
2312.05:425:39
2411.95:435:37
2511.95:435:36
2611.85:445:34
2711.85:455:33
2811.85:465:31
2911.75:475:30
3011.75:485:28

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.98 kWh/m².

For context, solar energy here swings from a low near 2.39 kWh/m² to a high of 5.74 kWh/m² in May across the year — September's 3.98 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.4Bright
24.4Bright
34.4Bright
44.3Bright
54.3Bright
64.3Bright
74.2Bright
84.2Bright
94.1Bright
104.1Bright
114.1Bright
124.0Bright
134.0Bright
144.0Moderate
154.0Moderate
163.9Moderate
173.9Moderate
183.9Moderate
193.9Moderate
203.8Moderate
213.8Moderate
223.8Moderate
233.8Moderate
243.7Moderate
253.7Moderate
263.7Moderate
273.7Moderate
283.6Moderate
293.6Moderate
303.6Moderate
Planning a trip in September

Hazard calendar for Ōmachi

In seasonPeak

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

Ōmachi 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 Ōmachi?

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

4.6
Sightseeing
2nd-best month of the year
2.1
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Ōmachi for sightseeing.

What to pack for Ōmachi in September

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

In September, Ōmachi sees daytime highs around 19°C and nights near 12°C. Pack rain gear. About 19 days see rain.

rain gear

Sea temperature near Ōmachi 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 61 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 18 to Nov 3 — about 4.6 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan13Bracing
Feb11Bracing
Mar10Bracing
Apr11Bracing
May15Cool
Jun20Cool
Jul24Refreshing
Aug27Warm
Sep25Warm
Oct22Refreshing
Nov19Cool
Dec16Cool

UV index in Ōmachi 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 Ōmachi peaks around July 20 at about 10 (extreme) — 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 highExtremeVery highModerateJul 20UV 10Dec 21UV 2
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr7Very high
May9Very high
Jun10Very high
Jul10Extreme
Aug10Extreme
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Ōmachi 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 Ōmachi is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (December, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1721 µg/m³Dec 1510 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar20Moderate
Apr21Moderate
May20Moderate
Jun18Moderate
Jul15Moderate
Aug13Moderate
Sep12Good
Oct11Good
Nov11Good
Dec10Good
Location & terrain

Where is Ōmachi?

Ōmachi sits at 36.5°N, 137.9°E, 714 m above sea level, in Japan. The nearest listed city is Hotaka, 18 km away.

Topography around Ōmachi

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

Within 3 km, the terrain around Ōmachi has significant variations in elevation — a maximum elevation change of 486 m around an average of 823 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,371 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,120 m.

The land around Ōmachi is covered by trees (50%) and artificial surfaces (26%) within 3 km, trees (83%) within 16 km, and trees (75%) within 80 km.

3 km
486 m
16 km
2,371 m
80 km
3,120 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Hotaka 18 km · Chikuma 20 km · Toyoshina 22 km · Azumino 24 km · Sakaki 29 km · Matsumoto 31 km · Nagano 33 km · Ueda 39 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 Ōmachi (36.5°, 137.8667°, elevation 714 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).