Saikai weather in September

In September, Saikai sees average daytime highs of 26°C and overnight lows near 23°C, with 188 mm of rain across 11.3 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 28°C in the first days to 25°C by the end. The sky is clear or mostly clear about 41% 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 Saikai's 3rd-clearest and 8th-windiest month. For the whole year in context, see Saikai's year-round climate.

Daytime high
26°
3rd warmest
Overnight low
23°
10th coldest
Rainfall
188 mm
11.3 wet days
Daylight
12 h 12 min
6:10 AM – 6:22 PM
Cloud cover
54%
3rd clearest
Wind
14 km/h
8th windiest
Solar energy
4.32 kWh/m²
Travel score
6.5
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 28°C in the first days to 25°C by the end.

A typical September day in Saikai reaches about 26°C in the afternoon and slips back to 23°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 24°C and 29°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)
12825
22825
32825
42825
52824
62824
72724
82724
92724
102724
112724
122724
132723
142723
152723
162623
172623
182623
192623
202622
212622
222622
232522
242522
252522
262522
272521
282521
292521
302421

How September really feels in Saikai

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.

Saikai 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° / 709.60.510.12.1
Feb10° / 8590.410.82.4
Mar13° / 13411.1011.73.6
Apr17° / 13°15810.7012.85.3
May21° / 17°17710.4013.76.3
Jun24° / 21°37215.8014.15.7
Jul27° / 25°30616.20145.3
Aug29° / 26°18214.1013.25.2
Sep26° / 23°18811.3012.26.5
Oct22° / 19°1096.7011.27.4
Nov17° / 14°988010.35.8
Dec12° / 819.209.93.3

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 41% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 13% of September, with mostly cloudy or overcast conditions the remaining 46%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15149
25248
35248
45347
55347
65347
75446
85446
95446
105545
115545
125545
135545
145545
155545
165545
175545
185545
195446
205446
215446
225446
235446
245446
255545
265545
275545
285644
295644
305743

Chance of precipitation in September

Any precipitation

Saikai gets around 188 mm of rain over 11.3 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 37% and peaks near 45% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
145
244
343
442
542
642
741
841
941
1040
1140
1239
1338
1438
1537
1637
1736
1836
1935
2034
2134
2233
2333
2432
2532
2631
2731
2830
2930
3029

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 72% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1003204730
2004214827
3004224825
4005244823
5006254721
6017264720
7018274618
8019284617
90110284515
100211294414
110213294213
120314304112
131316303911
141417303810
15151930369
16152030349
17262230328
18272330317
19282430296
20292530276
213102630265
223112730244
233122830234
243142929213
254153029203
264163029182
275183028172
285193028162
296203027151
307223026141

Wind in September

Winds average 14 km/h in September.

Across September, daily wind ranges from about 13 km/h on the calmest days to 14 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
113light breeze
213light breeze
313light breeze
413light breeze
513light breeze
613light breeze
713light breeze
813light breeze
913light breeze
1013light breeze
1113light breeze
1213light breeze
1314light breeze
1414light breeze
1514light breeze
1614light breeze
1714light breeze
1814light breeze
1914light breeze
2014light breeze
2114light breeze
2214light breeze
2314light breeze
2414light breeze
2514light breeze
2614light breeze
2714light breeze
2814light breeze
2914light breeze
3014light breeze

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 6:00 AM to 6:19 AM, and sunset from 6:42 PM to 6:02 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.76:006:42
212.76:006:41
312.66:016:40
412.66:026:38
512.66:026:37
612.56:036:36
712.56:046:34
812.56:046:33
912.46:056:31
1012.46:066:30
1112.46:066:29
1212.36:076:27
1312.36:086:26
1412.36:086:24
1512.26:096:23
1612.26:106:22
1712.26:106:20
1812.16:116:19
1912.16:126:17
2012.16:126:16
2112.06:136:15
2212.06:146:13
2312.06:146:12
2411.96:156:10
2511.96:166:09
2611.96:166:08
2711.86:176:06
2811.86:186:05
2911.76:196:03
3011.76:196:02

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.32 kWh/m².

For context, solar energy here swings from a low near 2.14 kWh/m² to a high of 5.41 kWh/m² in May across the year — September's 4.32 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.6Bright
34.6Bright
44.6Bright
54.6Bright
64.5Bright
74.5Bright
84.5Bright
94.5Bright
104.5Bright
114.5Bright
124.4Bright
134.4Bright
144.4Bright
154.4Bright
164.3Bright
174.3Bright
184.3Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.2Bright
244.2Bright
254.1Bright
264.1Bright
274.1Bright
284.1Bright
294.1Bright
304.0Bright
Planning a trip in September

Hazard calendar for Saikai

In seasonPeak

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

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

Saikai's rainy season runs May–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 Saikai?

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

6.5
Sightseeing
2nd-best month of the year
6.3
Beach & pool
2nd-best month of the year

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

What to pack for Saikai in September

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

In September, Saikai sees daytime highs around 26°C and nights near 23°C. Worth packing: light clothes and rain gear. About 11 days see rain.

light clothesrain gear

Sea temperature near Saikai 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 13 km away) is warmest in August at about 27°C and coldest in February near 15°C.

It's comfortable for a long swim from May 27 to Nov 29 — about 6.1 months when the water holds above 20°C.

15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan16Cool
Feb15Cool
Mar16Cool
Apr17Cool
May19Cool
Jun22Refreshing
Jul25Warm
Aug27Warm
Sep26Warm
Oct24Refreshing
Nov21Refreshing
Dec19Cool

UV index in Saikai 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 Saikai peaks around July 15 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 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 highVery highModerateJul 15UV 10Dec 21UV 3
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar6High
Apr7Very high
May8Very high
Jun9Very high
Jul10Extreme
Aug8Very high
Sep9Very high
Oct7High
Nov4Moderate
Dec3Moderate

Air quality in Saikai 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 Saikai is worst in April — around 24 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 11 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateModerateGoodModerateApr 1324 µg/m³Oct 1212 µg/m³
PM2.5 (µg/m³)Level
Jan16Moderate
Feb19Moderate
Mar23Moderate
Apr24Moderate
May21Moderate
Jun17Moderate
Jul12Good
Aug12Moderate
Sep12Good
Oct11Good
Nov14Moderate
Dec13Moderate
Location & terrain

Where is Saikai?

Saikai sits at 33.0°N, 129.7°E, 184 m above sea level, in Japan. The nearest listed city is Sasebo, 21 km away.

Topography around Saikai

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

Within 3 km, the terrain around Saikai has significant variations in elevation — a maximum elevation change of 353 m around an average of 182 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 564 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,455 m.

The land around Saikai is covered by trees (96%) within 3 km, water (55%) and trees (42%) within 16 km, and water (68%) and trees (24%) within 80 km.

3 km
353 m
16 km
564 m
80 km
1,455 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Sasebo 21 km · Togitsu 23 km · Ōmura 26 km · Obita 27 km · Arita 30 km · Nagasaki 32 km · Ureshinomachi-shimojuku 33 km · Imarichō-kō 37 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 Saikai (32.9839°, 129.6809°, elevation 184 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).