Yilan weather in September

In September, Yilan sees average daytime highs of 27°C and overnight lows near 24°C, with 336 mm of rain across 20.5 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 2nd-wettest month of the year here.

Highs ease over the month, from about 29°C in the first days to 26°C by the end. The sky is clear or mostly clear about 16% 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 Yilan's 2nd-clearest and 6th-windiest month. For the whole year in context, see Yilan's year-round climate.

Daytime high
27°
4th warmest
Overnight low
24°
9th coldest
Rainfall
336 mm
20.5 wet days
Daylight
12 h 06 min
5:43 AM – 5:52 PM
Cloud cover
70%
2nd clearest
Wind
8 km/h
6th windiest
Solar energy
4.54 kWh/m²
Travel score
4.6
out of 10

Yilan is A county-administered city in Yilan County, Taiwan.

Density
3,203/km²
people per km²
Founded
1945

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 29°C in the first days to 26°C by the end.

A typical September day in Yilan reaches about 27°C in the afternoon and slips back to 24°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 25°C and 30°C. Set against its neighbours, September runs about 2°C cooler than August and about 3°C warmer than October.

20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
12925
22924
32924
42924
52824
62824
72824
82824
92824
102824
112824
122824
132824
142824
152824
162724
172723
182723
192723
202723
212723
222723
232723
242723
252623
262623
272623
282623
292622
302622

How September really feels in Yilan

Once humidity and wind are folded in, September averages 1 day 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
1
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.

Yilan weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 2nd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan17° / 13°1902210.63.6
Feb17° / 13°16419.711.13.9
Mar19° / 15°15219.911.84.6
Apr22° / 18°18520.812.64.8
May25° / 21°29725.213.24.3
Jun28° / 24°31925.313.53.6
Jul30° / 25°27122.313.43.7
Aug29° / 25°32922.912.93.7
Sep27° / 24°33620.512.24.6
Oct24° / 21°39421.611.44.9
Nov21° / 18°3362110.84.6
Dec18° / 14°24421.710.54.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 16% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 19% of September, with mostly cloudy or overcast conditions the remaining 66%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13763
23664
33664
43664
53664
63664
73664
83862
93862
103862
113862
123862
133862
143763
153763
163664
173565
183367
193367
203268
213268
223268
233169
243070
252971
262971
273070
282971
292971
302971

Chance of precipitation in September

Any precipitation

Yilan gets around 336 mm of rain over 20.5 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 68% and peaks near 73% on the wettest days.

0%20%40%60%80%151015202530
Rain chance (%)
172
271
371
470
570
669
768
867
966
1066
1165
1265
1365
1465
1565
1666
1766
1867
1967
2068
2168
2269
2369
2470
2570
2671
2771
2872
2972
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 67% of days. Sticky, muggy-or-worse air turns up on roughly 93% of them.

0%25%50%75%100%151015202530
Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
10168112
20178111
30188011
40188110
50198010
60210799
70211789
80211789
90312778
100313768
110414757
120515737
130516736
140618706
150719695
160720685
170822655
180823654
191924624
201926604
211927594
2211028583
2311028583
2421029563
2521130543
2621130552
2731230532
2831230532
2931331512
3031431502

Wind in September

Winds average 8 km/h in September.

Across September, daily wind ranges from about 7 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
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
238calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

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 5:37 AM to 5:48 AM, and sunset from 6:08 PM to 5:36 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.55:376:08
212.55:386:07
312.55:386:06
412.45:396:05
512.45:396:04
612.45:396:03
712.45:406:02
812.35:406:00
912.35:405:59
1012.35:415:58
1112.35:415:57
1212.25:425:56
1312.25:425:55
1412.25:425:54
1512.25:435:53
1612.15:435:52
1712.15:435:50
1812.15:445:49
1912.15:445:48
2012.05:455:47
2112.05:455:46
2212.05:455:45
2312.05:465:44
2411.95:465:43
2511.95:465:42
2611.95:475:40
2711.95:475:39
2811.85:485:38
2911.85:485:37
3011.85:485:36

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.54 kWh/m².

For context, solar energy here swings from a low near 2.07 kWh/m² to a high of 5.81 kWh/m² in July across the year — September's 4.54 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
35.0Bright
44.9Bright
54.9Bright
64.9Bright
74.9Bright
84.8Bright
94.8Bright
104.8Bright
114.8Bright
124.7Bright
134.7Bright
144.7Bright
154.6Bright
164.6Bright
174.5Bright
184.5Bright
194.4Bright
204.4Bright
214.3Bright
224.3Bright
234.3Bright
244.2Bright
254.2Bright
264.1Bright
274.1Bright
284.0Bright
294.0Moderate
303.9Moderate
Planning a trip in September

Hazard calendar for Yilan

In seasonPeak

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

Yilan 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 Yilan?

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

4.6
Sightseeing
3rd-best month of the year
4.9
Beach & pool
2nd-best month of the year

September is a reasonable time to visit Yilan for sightseeing.

What to pack for Yilan in September

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

In September, Yilan sees daytime highs around 27°C and nights near 24°C. Pack light clothes and rain gear. Worth having: sun protection. About 21 days see rain.

light clothesrain gearsun protection

Sea temperature near Yilan 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 18 km away) is warmest in August at about 28°C and coldest in January near 22°C.

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

20°22°24°26°28°30°JanFebMarAprMayJunJulAugSepOctNovDecrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan22Refreshing
Feb22Refreshing
Mar23Refreshing
Apr24Warm
May26Warm
Jun27Warm
Jul28Tropical
Aug28Tropical
Sep28Warm
Oct26Warm
Nov25Warm
Dec23Refreshing

UV index in Yilan in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 11 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Yilan peaks around July 14 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 5 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecHighVery highExtremeVery highHighJul 14UV 11Dec 21UV 5
UV index (midday)Level
Jan6High
Feb8Very high
Mar9Very high
Apr7High
May10Extreme
Jun11Extreme
Jul12Extreme
Aug10Very high
Sep11Extreme
Oct8Very high
Nov7High
Dec5Moderate

Air quality in Yilan 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 Yilan is worst in April — around 52 µg/m³ PM2.5 (poor), about 2.1× the cleanest month (October, 25 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecPoorModerateApr 1052 µg/m³Oct 1626 µg/m³
PM2.5 (µg/m³)Level
Jan38Poor
Feb43Poor
Mar51Poor
Apr52Poor
May44Poor
Jun41Poor
Jul32Moderate
Aug32Moderate
Sep30Moderate
Oct25Moderate
Nov32Moderate
Dec32Moderate
Location & terrain

Where is Yilan?

Yilan sits at 24.8°N, 121.8°E, 15 m above sea level, in Taiwan. The nearest listed city is Xizhi, 36 km away.

XizhiNeihuTaipeiJiufenBanqiaoKeelungShulinSanxia

Topography around Yilan

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

Within 3 km, the terrain around Yilan has only modest variations in elevation — a maximum elevation change of 33 m around an average of 9 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,413 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,839 m.

The land around Yilan is covered by cropland (40%), artificial surfaces (35%) and trees (21%) within 3 km, trees (50%) and water (23%) within 16 km, and trees (47%) and water (46%) within 80 km.

3 km
33 m
16 km
1,413 m
80 km
3,839 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Xizhi 36 km · Neihu 40 km · Taipei 40 km · Jiufen 40 km · Banqiao 41 km · Keelung 42 km · Shulin 42 km · Sanxia 43 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 Yilan (24.757°, 121.753°, elevation 15 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).