Okaya weather in September

In September, Okaya sees average daytime highs of 23°C and overnight lows near 15°C, with 159 mm of rain across 12.8 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 25°C in the first days to 21°C by the end. The sky is clear or mostly clear about 19% 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 Okaya's 10th-clearest and 11th-windiest month. For the whole year in context, see Okaya's year-round climate.

Daytime high
23°
3rd warmest
Overnight low
15°
10th coldest
Rainfall
159 mm
12.8 wet days
Daylight
12 h 12 min
5:35 AM – 5:49 PM
Cloud cover
69%
10th clearest
Wind
5 km/h
11th windiest
Solar energy
4.09 kWh/m²
Travel score
6.1
out of 10

Okaya is city in Nagano Prefecture, Japan.

Density
638/km²
people per km²
Founded
1936

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 25°C in the first days to 21°C by the end.

A typical September day in Okaya reaches about 23°C in the afternoon and slips back to 15°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 19°C and 27°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°151015202530
Avg high (°C)Avg low (°C)
12617
22517
32517
42517
52517
62516
72516
82516
92416
102416
112416
122415
132415
142315
152315
162315
172314
182314
192214
202214
212214
222213
232213
242113
252113
262112
272112
282112
292012
302012

How September really feels in Okaya

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.

Okaya 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 / -8°8511.512.49.80.0
Feb / -7°8610.19.510.60.0
Mar / -3°14213.38.911.70.9
Apr14° / 12712.41.912.93.7
May19° / 13312.10.113.95.7
Jun22° / 14°17815.5014.45.4
Jul26° / 18°19817014.25.5
Aug27° / 18°12313.4013.45.9
Sep23° / 15°15912.8012.26.1
Oct17° / 17012.10.111.15.2
Nov11° / 9710.41.710.12.8
Dec / -4°84129.49.60.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 19% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 63%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13763
23763
33763
43664
53763
63763
73763
83763
93763
103763
113763
123763
133664
143664
153763
163763
173664
183664
193664
203565
213664
223664
233664
243664
253664
263664
273763
283763
293763
303763

Chance of precipitation in September

Any precipitation

Okaya gets around 159 mm of rain over 12.8 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 44% and peaks near 45% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
144
244
344
444
544
644
744
844
944
1044
1143
1243
1343
1443
1543
1643
1743
1843
1943
2043
2143
2243
2343
2443
2543
2644
2744
2845
2945
3045

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 36% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
18275411
29285310
310295110
41130509
51230499
61331478
71532467
81633447
91734426
101935405
112136385
122336364
132636344
142836323
153136303
163435283
173735262
184034242
194333222
204632201
214931181
225230171
235529151
245828131
256027121
266326101
27662590
28682480
29702370
30722260

Wind in September

Winds average 5 km/h in September.

Across September, daily wind ranges from about 5 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
15calm
25calm
35calm
45calm
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 5:23 AM to 5:47 AM, and sunset from 6:12 PM to 5:27 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:236:12
212.85:246:10
312.75:256:09
412.75:266:07
512.75:276:06
612.65:276:04
712.65:286:03
812.55:296:01
912.55:306:00
1012.55:315:58
1112.45:315:57
1212.45:325:55
1312.35:335:54
1412.35:345:52
1512.35:355:50
1612.25:355:49
1712.25:365:47
1812.15:375:46
1912.15:385:44
2012.15:395:43
2112.05:395:41
2212.05:405:40
2312.05:415:38
2411.95:425:37
2511.95:435:35
2611.85:435:34
2711.85:445:32
2811.85:455:30
2911.75:465:29
3011.75:475:27

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 2.54 kWh/m² to a high of 5.73 kWh/m² in May across the year — September's 4.09 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.5Bright
24.5Bright
34.5Bright
44.4Bright
54.4Bright
64.4Bright
74.3Bright
84.3Bright
94.3Bright
104.2Bright
114.2Bright
124.2Bright
134.1Bright
144.1Bright
154.1Bright
164.0Bright
174.0Bright
184.0Bright
194.0Moderate
203.9Moderate
213.9Moderate
223.9Moderate
233.9Moderate
243.8Moderate
253.8Moderate
263.8Moderate
273.8Moderate
283.7Moderate
293.7Moderate
303.7Moderate
Planning a trip in September

Hazard calendar for Okaya

In seasonPeak

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

Okaya 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 Okaya?

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

6.1
Sightseeing
1st-best month of the year
4.6
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Okaya for sightseeing.

What to pack for Okaya in September

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

In September, Okaya sees daytime highs around 23°C and nights near 15°C. Worth packing: light clothes and rain gear. About 13 days see rain.

light clothesrain gear

UV index in Okaya 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 Okaya peaks around July 14 at about 11 (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 14UV 11Dec 21UV 2
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr7Very high
May9Very high
Jun10Extreme
Jul11Extreme
Aug10Very high
Sep9Very high
Oct6High
Nov4Moderate
Dec2Moderate

Air quality in Okaya 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 Okaya is worst in April — around 18 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1918 µg/m³Dec 178 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb11Good
Mar17Moderate
Apr18Moderate
May17Moderate
Jun16Moderate
Jul13Moderate
Aug12Good
Sep10Good
Oct10Good
Nov9Good
Dec8Good
Location & terrain

Where is Okaya?

Okaya sits at 36.1°N, 138.0°E, 773 m above sea level, in Japan. The nearest listed city is Shimosuwa, 4.0 km away.

Topography around Okaya

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

Within 3 km, the terrain around Okaya has significant variations in elevation — a maximum elevation change of 374 m around an average of 856 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,313 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,030 m.

The land around Okaya is covered by trees (45%) and artificial surfaces (36%) within 3 km, trees (73%) within 16 km, and trees (87%) within 80 km.

3 km
374 m
16 km
1,313 m
80 km
3,030 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Shimosuwa 4.0 km · Suwa 6.0 km · Shiojiri 9.0 km · Tatsuno 9.0 km · Chino 12 km · Kinoshita 18 km · Matsumoto 21 km · Minamiminowa 21 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 Okaya (36.0566°, 138.0451°, elevation 773 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). 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).