Chiayi City weather in September

In September, Chiayi City sees average daytime highs of 29°C and overnight lows near 23°C, with 436 mm of rain across 24 wet days and about 12.1 hours of daylight. It is the 4th-warmest and 3rd-wettest month of the year here.

Day-to-day highs hold fairly steady near 29°C through the month. The sky is clear or mostly clear about 12% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 h 30 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Chiayi City's 8th-clearest and 9th-windiest month. For the whole year in context, see Chiayi City's year-round climate.

Daytime high
29°
4th warmest
Overnight low
23°
9th coldest
Rainfall
436 mm
24 wet days
Daylight
12 h 06 min
5:48 AM – 5:57 PM
Cloud cover
71%
8th clearest
Wind
6 km/h
9th windiest
Solar energy
4.73 kWh/m²
Travel score
3.6
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 29°C through the month.

A typical September day in Chiayi City reaches about 29°C in the afternoon and slips back to 23°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 27°C and 30°C. Set against its neighbours, September runs on par with August and about 2°C warmer than October.

15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
12923
22923
32923
42923
52923
62923
72923
82923
92923
102923
112923
122923
132923
142923
152923
162923
172923
182923
192923
202923
212922
222922
232922
242922
252922
262922
272822
282822
292822
302822

How September really feels in Chiayi City

Once humidity and wind are folded in, September averages 15 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
15
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.

Chiayi City weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan20° / 12°531010.76.6
Feb21° / 13°6211.611.26.3
Mar24° / 16°8513.311.86.4
Apr26° / 19°1441612.55.7
May28° / 21°27022.113.14.3
Jun29° / 23°36524.213.43.3
Jul30° / 24°55526.713.33.0
Aug30° / 24°66728.512.82.9
Sep29° / 23°4362412.13.6
Oct27° / 20°20718.611.45.3
Nov25° / 18°811210.96.7
Dec22° / 14°6010.710.66.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 12% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 22% of September, with mostly cloudy or overcast conditions the remaining 67%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
12179
22179
32278
42278
52278
62377
72476
82575
92674
102674
112971
122971
133070
143268
153367
163466
173664
183664
193763
203961
214060
224159
234159
244258
254456
264456
274555
284654
294753
304753

Chance of precipitation in September

Any precipitation

Chiayi City gets around 436 mm of rain over 24 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 80% and peaks near 88% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%100%151015202530
Rain chance (%)
188
288
387
487
587
686
786
885
984
1084
1183
1282
1381
1481
1580
1679
1779
1878
1977
2077
2176
2276
2375
2475
2575
2675
2774
2874
2974
3073

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 81% of days. Sticky, muggy-or-worse air turns up on roughly 99% of them.

0%25%50%75%100%151015202530
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
104915
205914
305914
415913
516903
616903
717893
818883
918883
1019873
11110872
12111862
13113833
14114823
15115813
16116803
17117793
18118783
19119773
20119782
21120772
22121762
23222742
24222742
25223732
26324712
27324721
28425701
29426691
30527671

Wind in September

Winds average 6 km/h in September.

Across September, daily wind ranges from about 5 km/h on the calmest days to 6 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
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 30 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 42 minutes over September. Sunrise moves from 5:44 AM to 5:53 AM, and sunset from 6:12 PM to 5:42 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.55:446:12
212.55:446:11
312.45:446:10
412.45:456:09
512.45:456:08
612.45:456:07
712.35:466:06
812.35:466:05
912.35:466:04
1012.35:476:03
1112.35:476:02
1212.25:476:01
1312.25:486:00
1412.25:485:59
1512.25:485:58
1612.15:485:57
1712.15:495:55
1812.15:495:54
1912.15:495:53
2012.05:505:52
2112.05:505:51
2212.05:505:50
2312.05:515:49
2411.95:515:48
2511.95:525:47
2611.95:525:46
2711.95:525:45
2811.95:535:44
2911.85:535:43
3011.85:535:42

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.73 kWh/m².

For context, solar energy here swings from a low near 3.6 kWh/m² to a high of 5.62 kWh/m² in April across the year — September's 4.73 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.7Bright
34.7Bright
44.7Bright
54.7Bright
64.7Bright
74.7Bright
84.7Bright
94.7Bright
104.8Bright
114.8Bright
124.8Bright
134.8Bright
144.8Bright
154.8Bright
164.8Bright
174.8Bright
184.8Bright
194.7Bright
204.7Bright
214.7Bright
224.7Bright
234.7Bright
244.7Bright
254.7Bright
264.7Bright
274.6Bright
284.6Bright
294.6Bright
304.6Bright
Planning a trip in September

Hazard calendar for Chiayi City

In seasonPeak

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

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

Chiayi City's monsoon runs June–September, when most of the year's rain falls.

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

Is September a good time to visit Chiayi City?

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

3.6
Sightseeing
9th-best month of the year
4.6
Beach & pool
7th-best month of the year

September is a weaker month for outdoor sightseeing in Chiayi City.

What to pack for Chiayi City in September

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

In September, Chiayi City sees daytime highs around 29°C and nights near 23°C. Pack light clothes and rain gear. Worth having: sun protection. About 24 days see rain.

light clothesrain gearsun protection

Sea temperature near Chiayi City in September

The nearest coast averages about 28°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 35 km away) is warmest in July at about 29°C and coldest in January near 22°C.

The water stays above 20°C all year — warm enough for a swim any month.

20°25°30°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan22Refreshing
Feb22Refreshing
Mar23Refreshing
Apr25Warm
May27Warm
Jun28Tropical
Jul29Tropical
Aug29Tropical
Sep28Tropical
Oct27Warm
Nov25Warm
Dec23Refreshing

UV index in Chiayi City 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 Chiayi City peaks around June 17 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 6 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecHighVery highExtremeVery highHighJun 17UV 12Dec 20UV 6
UV index (midday)Level
Jan6High
Feb8Very high
Mar10Very high
Apr8Very high
May10Very high
Jun12Extreme
Jul10Extreme
Aug11Extreme
Sep9Very high
Oct7Very high
Nov7High
Dec6High

Air quality in Chiayi City 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 Chiayi City is worst in March — around 40 µg/m³ PM2.5 (poor), about 1.7× the cleanest month (July, 23 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecPoorModerateMar 1739 µg/m³Jul 1323 µg/m³
PM2.5 (µg/m³)Level
Jan36Poor
Feb36Poor
Mar40Poor
Apr36Poor
May28Moderate
Jun24Moderate
Jul23Moderate
Aug25Moderate
Sep31Moderate
Oct33Moderate
Nov34Moderate
Dec33Moderate
Location & terrain

Where is Chiayi City?

Chiayi City sits at 23.5°N, 120.4°E, 45 m above sea level, in Taiwan. The nearest listed city is Taibao, 12 km away.

XinyingDouliuCitongBudaiErlun

Topography around Chiayi City

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

Within 3 km, the terrain around Chiayi City has only modest variations in elevation — a maximum elevation change of 84 m around an average of 40 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 860 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,887 m.

The land around Chiayi City is covered by artificial surfaces (65%) and trees (23%) within 3 km, trees (46%) and cropland (37%) within 16 km, and trees (47%) and water (32%) within 80 km.

3 km
84 m
16 km
860 m
80 km
3,887 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Taibao 12 km · Xingang 14 km · Beigang 18 km · Xinying 24 km · Douliu 27 km · Citong 31 km · Budai 31 km · Erlun 33 km

Taiwan travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B
110 / 220 V · 60 Hz
Happiness
6.7 / 10
World Happiness, 2025
Religion
Buddhist 35%Taoist 33%none or unspecified 18%folk religion approximately 10%

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 Chiayi City (23.4792°, 120.4489°, elevation 45 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).