Aki weather in September

In September, Aki sees average daytime highs of 26°C and overnight lows near 21°C, with 302 mm of rain across 16.9 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 27°C in the first days to 24°C by the end. The sky is clear or mostly clear about 27% 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 Aki's 8th-clearest and 8th-windiest month. For the whole year in context, see Aki's year-round climate.

Daytime high
26°
3rd warmest
Overnight low
21°
10th coldest
Rainfall
302 mm
16.9 wet days
Daylight
12 h 12 min
5:53 AM – 6:05 PM
Cloud cover
64%
8th clearest
Wind
10 km/h
8th windiest
Solar energy
4.41 kWh/m²
Travel score
5.5
out of 10

Aki is city in Kōchi Prefecture, Japan.

Density
52/km²
people per km²
Founded
1954

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 27°C in the first days to 24°C by the end.

A typical September day in Aki reaches about 26°C in the afternoon and slips back to 21°C overnight — a 5°C spread between the day's warmth and the night's chill. On most days the high lands between 24°C and 28°C. Set against its neighbours, September runs about 2°C cooler than August and about 4°C warmer than October.

15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12823
22823
32723
42723
52723
62723
72723
82722
92722
102722
112722
122722
132622
142622
152622
162621
172621
182621
192621
202621
212521
222520
232520
242520
252520
262520
272520
282520
292419
302419

How September really feels in Aki

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.

Aki 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° / 776.40.5102.3
Feb10° / 1017.80.910.82.5
Mar13° / 16711.20.111.73.8
Apr18° / 11°20311.6012.85.4
May21° / 16°23612.7013.76.0
Jun24° / 20°35819.1014.25.1
Jul27° / 23°35320.30144.7
Aug28° / 24°26119.6013.24.6
Sep26° / 21°30216.9012.25.5
Oct22° / 16°21711.3011.26.6
Nov17° / 11°1188.1010.35.8
Dec12° / 876.109.83.6

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 27% 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 56%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14258
24258
34159
44258
54258
64357
74258
84258
94258
104258
114357
124456
134456
144456
154456
164456
174555
184555
194654
204555
214555
224555
234654
244654
254555
264654
274654
284753
294654
304654

Chance of precipitation in September

Any precipitation

Aki gets around 302 mm of rain over 16.9 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 56% and peaks near 64% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
164
264
363
463
563
662
762
862
961
1061
1160
1260
1359
1458
1557
1657
1756
1855
1954
2053
2152
2252
2351
2450
2549
2648
2748
2847
2947
3046

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 34% of days. Sticky, muggy-or-worse air turns up on roughly 65% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
101825624
201926613
301927603
4011029573
5021130552
6021131542
7031232512
8031333492
9141434471
10151435451
11151535421
12261635401
13281736371
14291835351
153101935331
164112034311
174122134280
185132233260
196152232250
207162331230
218172430210
228182529190
239192528180
2410202627160
2511212727150
2611212826140
2712222825120
2813222924110
2914232923100
301523302290

Wind in September

Winds average 10 km/h in September.

Across September, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
19calm
29calm
39calm
49calm
59calm
69calm
79calm
89calm
99calm
109calm
1110calm
1210calm
1310calm
1410calm
1510calm
1610calm
1710calm
1810calm
1910calm
2010calm
2110calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm

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 5:42 AM to 6:03 AM, and sunset from 6:26 PM to 5:45 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:426:26
212.75:436:25
312.75:446:23
412.65:446:22
512.65:456:20
612.65:466:19
712.55:466:18
812.55:476:16
912.55:486:15
1012.45:486:13
1112.45:496:12
1212.35:506:11
1312.35:516:09
1412.35:516:08
1512.25:526:06
1612.25:536:05
1712.25:536:03
1812.15:546:02
1912.15:556:01
2012.15:555:59
2112.05:565:58
2212.05:575:56
2312.05:575:55
2411.95:585:53
2511.95:595:52
2611.86:005:51
2711.86:005:49
2811.86:015:48
2911.76:025:46
3011.76:035:45

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.41 kWh/m².

For context, solar energy here swings from a low near 2.64 kWh/m² to a high of 5.62 kWh/m² in May across the year — September's 4.41 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
34.9Bright
44.9Bright
54.8Bright
64.8Bright
74.8Bright
84.7Bright
94.7Bright
104.6Bright
114.6Bright
124.6Bright
134.5Bright
144.5Bright
154.5Bright
164.4Bright
174.4Bright
184.3Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.2Bright
244.1Bright
254.1Bright
264.1Bright
274.0Bright
284.0Bright
294.0Moderate
304.0Moderate
Planning a trip in September

Hazard calendar for Aki

In seasonPeak

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

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

Aki's rainy season runs March–October, 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 Aki?

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

5.5
Sightseeing
4th-best month of the year
5.3
Beach & pool
2nd-best month of the year

September is a reasonable time to visit Aki for sightseeing.

What to pack for Aki in September

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

In September, Aki sees daytime highs around 26°C and nights near 21°C. Pack rain gear. Worth having: light clothes. About 17 days see rain.

rain gearlight clothes

Sea temperature near Aki in September

The nearest coast averages about 27°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 14 km away) is warmest in August at about 28°C and coldest in February near 17°C.

It's comfortable for a long swim from May 3 to Dec 19 — about 7.6 months when the water holds above 20°C.

15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan18Cool
Feb17Cool
Mar18Cool
Apr19Cool
May21Refreshing
Jun23Refreshing
Jul26Warm
Aug28Warm
Sep27Warm
Oct25Warm
Nov23Refreshing
Dec20Refreshing

UV index in Aki in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Aki peaks around June 23 at about 11 (extreme) — 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 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highModerateJun 23UV 11Dec 22UV 3
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr8Very high
May9Very high
Jun11Extreme
Jul11Extreme
Aug9Very high
Sep10Very high
Oct7High
Nov4Moderate
Dec3Moderate

Air quality in Aki 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 Aki is worst in April — around 20 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (September, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodApr 1320 µg/m³Sep 2010 µg/m³
PM2.5 (µg/m³)Level
Jan12Moderate
Feb15Moderate
Mar19Moderate
Apr20Moderate
May18Moderate
Jun15Moderate
Jul11Good
Aug11Good
Sep10Good
Oct10Good
Nov11Good
Dec11Good
Location & terrain

Where is Aki?

Aki sits at 33.5°N, 133.9°E, 13 m above sea level, in Japan. The nearest listed city is Yamashita, 20 km away.

Topography around Aki

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

Within 3 km, the terrain around Aki has significant variations in elevation — a maximum elevation change of 426 m around an average of 37 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 1,031 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,939 m.

The land around Aki is covered by water (45%) and trees (23%) within 3 km, trees (53%) and water (42%) within 16 km, and trees (54%) and water (41%) within 80 km.

3 km
426 m
16 km
1,031 m
80 km
1,939 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Yamashita 20 km · Tosayamadachō-nakano 23 km · Nankoku 24 km · Muroto-misakicho 34 km · Kochi 34 km · Tosa 42 km · Ino 44 km · Susaki 58 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 Aki (33.5°, 133.9°, elevation 13 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).