Koga weather in September

In September, Koga sees average daytime highs of 28°C and overnight lows near 22°C, with 174 mm of rain across 12.8 wet days and about 12.2 hours of daylight. It is the 3rd-warmest and 3rd-wettest month of the year here.

Highs ease over the month, from about 30°C in the first days to 26°C by the end. The sky is clear or mostly clear about 32% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 h 42 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Koga's 4th-clearest and 7th-windiest month. For the whole year in context, see Koga's year-round climate.

Daytime high
28°
3rd warmest
Overnight low
22°
10th coldest
Rainfall
174 mm
12.8 wet days
Daylight
12 h 12 min
6:06 AM – 6:19 PM
Cloud cover
61%
4th clearest
Wind
11 km/h
7th windiest
Solar energy
4.24 kWh/m²
Travel score
5.5
out of 10

Koga is city in Fukuoka Prefecture, Japan.

Density
1,397/km²
people per km²
Founded
1997

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 30°C in the first days to 26°C by the end.

A typical September day in Koga reaches about 28°C in the afternoon and slips back to 22°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 25°C and 31°C. Set against its neighbours, September runs about 4°C cooler than August and about 5°C warmer than October.

15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13024
23024
33024
43023
53023
63023
73023
82923
92923
102923
112922
122922
132922
142822
152822
162822
172821
182821
192821
202821
212721
222721
232720
242720
252720
262720
272620
282619
292619
302619

How September really feels in Koga

Once humidity and wind are folded in, September averages 7 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
7
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Koga weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan10° / 629.91.2102.2
Feb11° / 659.20.810.72.7
Mar14° / 10811.30.211.74.1
Apr19° / 11°11910.5012.86.0
May24° / 16°13110013.76.8
Jun27° / 20°25314.3014.25.6
Jul30° / 24°249160144.0
Aug32° / 25°15514.5013.33.6
Sep28° / 22°17412.8012.25.5
Oct23° / 16°957.6011.27.3
Nov18° / 11°828.4010.25.9
Dec12° / 669.20.39.83.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 32% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 52%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14456
24555
34555
44555
54555
64654
74654
84654
94753
104753
114753
124753
134852
144852
154852
164852
174852
184852
194852
204852
214852
224852
234951
244951
254951
264951
274951
285149
295149
305149

Chance of precipitation in September

Any precipitation

Koga gets around 174 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 42% and peaks near 51% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
151
251
351
450
550
649
749
848
947
1047
1146
1245
1344
1442
1541
1641
1740
1839
1938
2038
2137
2236
2336
2435
2535
2634
2734
2833
2933
3032

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 32% of days. Sticky, muggy-or-worse air turns up on roughly 66% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1017245414
2017265313
3018275212
4019285111
50110295010
6011230489
7011330478
8021431458
9021532447
10031632426
11141732406
12151932395
13152032375
14172132354
15282232334
16292331314
172102431303
183112531283
193122630263
204132730243
214142729232
225152829212
236162928202
246172928182
257183027171
268193026151
279203026141
2810213125131
2912213124121
3013223023111

Wind in September

Winds average 11 km/h in September.

Across September, daily wind ranges from about 10 km/h on the calmest days to 11 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
510calm
611calm
711calm
811calm
911calm
1011calm
1111calm
1211calm
1311calm
1411calm
1511calm
1611calm
1711calm
1811calm
1911calm
2011calm
2111calm
2211calm
2311calm
2411calm
2511calm
2611calm
2711calm
2811calm
2911calm
3011calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 42 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 60 minutes over September. Sunrise moves from 5:56 AM to 6:16 AM, and sunset from 6:40 PM to 5:59 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:566:40
212.75:566:39
312.75:576:37
412.65:586:36
512.65:596:34
612.65:596:33
712.56:006:32
812.56:016:30
912.56:016:29
1012.46:026:27
1112.46:036:26
1212.36:036:24
1312.36:046:23
1412.36:056:22
1512.26:066:20
1612.26:066:19
1712.26:076:17
1812.16:086:16
1912.16:086:14
2012.16:096:13
2112.06:106:11
2212.06:116:10
2312.06:116:09
2411.96:126:07
2511.96:136:06
2611.86:136:04
2711.86:146:03
2811.86:156:01
2911.76:166:00
3011.76:165:59

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.24 kWh/m².

For context, solar energy here swings from a low near 2.14 kWh/m² to a high of 5.51 kWh/m² in May across the year — September's 4.24 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.6Bright
24.6Bright
34.5Bright
44.5Bright
54.5Bright
64.5Bright
74.5Bright
84.4Bright
94.4Bright
104.4Bright
114.4Bright
124.3Bright
134.3Bright
144.3Bright
154.3Bright
164.3Bright
174.2Bright
184.2Bright
194.2Bright
204.2Bright
214.1Bright
224.1Bright
234.1Bright
244.1Bright
254.0Bright
264.0Bright
274.0Bright
284.0Moderate
294.0Moderate
303.9Moderate
Planning a trip in September

Hazard calendar for Koga

In seasonPeak

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

Koga sits in the Pacific typhoon belt; the season peaks July–October.

Koga's rainy season runs April–September, when most of the year's rain falls.

Pacific typhoon
Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Koga?

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

5.5
Sightseeing
6th-best month of the year
6.3
Beach & pool
1st-best month of the year

September is a reasonable time to visit Koga for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Koga in September

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

In September, Koga sees daytime highs around 28°C and nights near 22°C. Pack light clothes. Worth having: rain gear. About 13 days see rain.

light clothesrain gear

Sea temperature near Koga in September

The nearest coast averages about 26°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 18 km away) is warmest in August at about 27°C and coldest in February near 14°C.

It's comfortable for a long swim from Jun 7 to Nov 20 — about 5.5 months when the water holds above 20°C.

10°15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan16Cool
Feb14Bracing
Mar14Bracing
Apr15Cool
May18Cool
Jun21Refreshing
Jul25Warm
Aug27Warm
Sep26Warm
Oct23Refreshing
Nov20Refreshing
Dec18Cool

UV index in Koga 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 Koga peaks around July 21 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 3 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJul 21UV 9Dec 22UV 3
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar6High
Apr8Very high
May8Very high
Jun7Very high
Jul9Very high
Aug9Very high
Sep9Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Koga 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 Koga is worst in April — around 25 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 12 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateApr 1225 µg/m³Oct 1212 µg/m³
PM2.5 (µg/m³)Level
Jan17Moderate
Feb20Moderate
Mar25Moderate
Apr25Moderate
May23Moderate
Jun18Moderate
Jul13Moderate
Aug15Moderate
Sep13Moderate
Oct12Moderate
Nov15Moderate
Dec14Moderate
Location & terrain

Where is Koga?

Koga sits at 33.7°N, 130.5°E, 10 m above sea level, in Japan. The nearest listed city is Nishifukuma, 4.0 km away.

Topography around Koga

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

Within 3 km, the terrain around Koga has only modest variations in elevation — a maximum elevation change of 108 m around an average of 13 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 674 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,246 m.

The land around Koga is covered by artificial surfaces (43%) and water (30%) within 3 km, water (42%) and trees (32%) within 16 km, and water (51%) and trees (34%) within 80 km.

3 km
108 m
16 km
674 m
80 km
1,246 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Nishifukuma 4.0 km · Shingū 4.0 km · Fukutsu 6.0 km · Munakata 11 km · Wakasugi 15 km · Sasaguri 15 km · Fukuoka 16 km · Sue 16 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 Koga (33.7333°, 130.4667°, elevation 10 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).