Shonai weather in September

In September, Shonai sees average daytime highs of 24°C and overnight lows near 17°C, with 170 mm of rain across 15.8 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 26°C in the first days to 21°C by the end. The sky is clear or mostly clear about 18% of the time in September, and the air most often feels humid.

Daylight stretches from about 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Shonai's 6th-clearest and 9th-windiest month. For the whole year in context, see Shonai's year-round climate.

Daytime high
24°
3rd warmest
Overnight low
17°
10th coldest
Rainfall
170 mm
15.8 wet days
Daylight
12 h 12 min
5:27 AM – 5:42 PM
Cloud cover
69%
6th clearest
Wind
8 km/h
9th windiest
Solar energy
3.71 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 26°C in the first days to 21°C by the end.

A typical September day in Shonai reaches about 24°C in the afternoon and slips back to 17°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 20°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°35°151015202530
Avg high (°C)Avg low (°C)
12620
22620
32619
42619
52619
62519
72519
82519
92519
102518
112518
122418
132418
142417
152417
162417
172317
182317
192316
202316
212316
222216
232215
242215
252215
262115
272114
282114
292114
302114

How September really feels in Shonai

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.

Shonai weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -2°19026.224.99.60.0
Feb / -2°13521.719.710.50.0
Mar / 14320.313.711.70.5
Apr13° / 11815.12.8133.1
May19° / 11°12513.6014.15.5
Jun23° / 16°14413.5014.75.9
Jul26° / 20°24718.2014.45.3
Aug27° / 21°20017.3013.55.3
Sep24° / 17°17015.8012.35.6
Oct18° / 11°17516.50114.8
Nov11° / 17319.54.59.92.2
Dec / 20625.118.19.30.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 18% 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 65%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13763
23763
33664
43763
53763
63763
73763
83763
93664
103763
113763
123763
133664
143664
153565
163565
173565
183466
193466
203466
213466
223466
233466
243466
253466
263466
273466
283367
293466
303466

Chance of precipitation in September

Any precipitation

Shonai gets around 170 mm of rain over 15.8 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 54% and peaks near 56% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
156
256
356
456
556
656
756
856
956
1056
1156
1255
1355
1455
1554
1654
1753
1853
1953
2052
2152
2252
2352
2452
2552
2653
2753
2853
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 28% of days. Sticky, muggy-or-worse air turns up on roughly 35% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1092339262
2092439252
31102539232
41102740211
51112839201
61122839181
72132939171
82143038161
93153037151
103163136131
114173135121
125183234110
137203132100
14821313090
151022312880
161124312670
171325312470
181526312260
191728302050
201929301840
212130291640
222331291430
232532281230
242733271120
25293426920
26313425810
27333524710
28353623610
29373621500
30393620400

Wind in September

Winds average 8 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
168calm
178calm
188calm
198calm
208calm
218calm
228calm
238calm
248calm
258calm
268calm
279calm
289calm
299calm
309calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over September. Sunrise moves from 5:13 AM to 5:40 AM, and sunset from 6:07 PM to 5:19 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:136:07
212.85:146:05
312.85:156:04
412.85:166:02
512.75:176:00
612.75:185:59
712.65:195:57
812.65:205:55
912.55:215:54
1012.55:225:52
1112.55:235:50
1212.45:245:49
1312.45:245:47
1412.35:255:46
1512.35:265:44
1612.25:275:42
1712.25:285:41
1812.25:295:39
1912.15:305:37
2012.15:315:35
2112.05:325:34
2212.05:335:32
2311.95:345:31
2411.95:355:29
2511.95:365:27
2611.85:375:26
2711.85:385:24
2811.75:385:22
2911.75:395:21
3011.65:405:19

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.71 kWh/m².

For context, solar energy here swings from a low near 1.62 kWh/m² to a high of 5.36 kWh/m² in May across the year — September's 3.71 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.1Bright
24.1Bright
34.0Bright
44.0Bright
54.0Moderate
64.0Moderate
73.9Moderate
83.9Moderate
93.9Moderate
103.8Moderate
113.8Moderate
123.8Moderate
133.7Moderate
143.7Moderate
153.7Moderate
163.6Moderate
173.6Moderate
183.6Moderate
193.6Moderate
203.6Moderate
213.5Moderate
223.5Moderate
233.5Moderate
243.5Moderate
253.5Moderate
263.4Moderate
273.4Moderate
283.4Moderate
293.4Moderate
303.3Moderate
Planning a trip in September

Hazard calendar for Shonai

In seasonPeak

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

Shonai 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 Shonai?

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

5.6
Sightseeing
2nd-best month of the year
4.5
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Shonai for sightseeing.

What to pack for Shonai in September

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

In September, Shonai sees daytime highs around 24°C and nights near 17°C. Pack rain gear. Worth having: light clothes. About 16 days see rain.

rain gearlight clothes

Sea temperature near Shonai 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 24 km away) is warmest in August at about 26°C and coldest in March near 9°C.

It's comfortable for a long swim from Jun 25 to Oct 26 — about 4.1 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan12Bracing
Feb10Bracing
Mar9Bracing
Apr10Bracing
May14Bracing
Jun19Cool
Jul23Refreshing
Aug26Warm
Sep25Warm
Oct21Refreshing
Nov18Cool
Dec15Bracing

UV index in Shonai in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Shonai peaks around August 17 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowAug 17UV 9Dec 19UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun8Very high
Jul7High
Aug9Very high
Sep7Very high
Oct5Moderate
Nov3Moderate
Dec2Low

Air quality in Shonai 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 Shonai is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.4× the cleanest month (December, 9 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1721 µg/m³Dec 159 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar19Moderate
Apr21Moderate
May20Moderate
Jun15Moderate
Jul13Moderate
Aug11Good
Sep10Good
Oct10Good
Nov10Good
Dec9Good
Location & terrain

Where is Shonai?

Shonai sits at 38.8°N, 139.9°E, 7 m above sea level, in Japan. The nearest listed city is Sakata, 9.0 km away.

Topography around Shonai

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

Within 3 km, the terrain around Shonai has only modest variations in elevation — a maximum elevation change of 14 m around an average of 8 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 776 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,205 m.

The land around Shonai is covered by cropland (77%) within 3 km, cropland (37%) and trees (36%) within 16 km, and trees (55%) and water (35%) within 80 km.

3 km
14 m
16 km
776 m
80 km
2,205 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Sakata 9.0 km · Tsuruoka 16 km · Shinjō 36 km · Nikaho 47 km · Obanazawa 51 km · Yachi 59 km · Murayama 61 km · Yurihonjō 62 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 Shonai (38.8485°, 139.9031°, elevation 7 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).