Ansan weather in September

In September, Ansan sees average daytime highs of 24°C and overnight lows near 19°C, with 127 mm of rain across 7.3 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 25°C in the first days to 22°C by the end. The sky is clear or mostly clear about 43% of the time in September, and the air most often feels humid.

Daylight stretches from about 12 h 48 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Ansan's 7th-clearest and 10th-windiest month. For the whole year in context, see Ansan's year-round climate.

Daytime high
24°
3rd warmest
Overnight low
19°
10th coldest
Rainfall
127 mm
7.3 wet days
Daylight
12 h 12 min
6:20 AM – 6:34 PM
Cloud cover
52%
7th clearest
Wind
12 km/h
10th windiest
Solar energy
4.26 kWh/m²
Travel score
7.3
out of 10

Ansan is city in South Korea.

Density
4,172/km²
people per km²
Founded
1986

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 25°C in the first days to 22°C by the end.

A typical September day in Ansan reaches about 24°C in the afternoon and slips back to 19°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 21°C and 26°C. Set against its neighbours, September runs about 3°C cooler than August and about 5°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12522
22522
32522
42521
52521
62521
72521
82521
92521
102420
112420
122420
132420
142420
152420
162420
172419
182319
192319
202319
212319
222318
232318
242218
252218
262218
272217
282217
292217
302117

How September really feels in Ansan

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.

Ansan weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -3°234.12.59.70.0
Feb / -1°304.31.310.60.0
Mar / 426.10.911.71.1
Apr12° / 797.3012.93.6
May17° / 13°1047.70145.9
Jun22° / 18°1277.6014.56.8
Jul25° / 22°29814.4014.36.0
Aug27° / 23°23912.8013.46.2
Sep24° / 19°1277.3012.37.3
Oct18° / 13°625.60116.7
Nov11° / 578.20.3103.1
Dec / -0°285.81.89.50.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 43% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 12% of September, with mostly cloudy or overcast conditions the remaining 45%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15050
25050
35149
45149
55248
65248
75248
85347
95347
105347
115446
125347
135347
145446
155446
165446
175644
185644
195644
205644
215743
225743
235743
245743
255743
265842
275842
285842
295941
305941

Chance of precipitation in September

Any precipitation

Ansan gets around 127 mm of rain over 7.3 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 26% and peaks near 36% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
136
235
334
432
531
631
730
829
928
1028
1127
1227
1326
1426
1525
1624
1724
1823
1922
2022
2122
2221
2321
2421
2521
2621
2721
2821
2921
3020

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the humid band about 28% of days. Sticky, muggy-or-worse air turns up on roughly 37% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1151940323
2162140302
3272240282
4282340251
5292440231
63102540211
73112640201
84122739180
95142738160
105152837140
116172836130
128182935110
139192933100
141020293190
151122302980
161323302770
171424302660
181525312450
191726312250
201827312040
211928311830
222129311630
232330311520
242430301320
252631301210
262831291010
27303228910
28323227810
29353225800
30373224700

Wind in September

Winds average 12 km/h in September.

Across September, daily wind ranges from about 12 km/h on the calmest days to 13 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
112light breeze
212light breeze
312light breeze
412calm
512calm
612calm
712calm
812calm
912calm
1012calm
1112light breeze
1212light breeze
1312light breeze
1412light breeze
1512light breeze
1612light breeze
1712light breeze
1812light breeze
1912light breeze
2012light breeze
2112light breeze
2212light breeze
2312light breeze
2412light breeze
2512light breeze
2612light breeze
2712light breeze
2813light breeze
2913light breeze
3013light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 48 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 66 minutes over September. Sunrise moves from 6:07 AM to 6:32 AM, and sunset from 6:58 PM to 6:12 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.86:076:58
212.86:086:56
312.86:096:55
412.76:106:53
512.76:116:52
612.66:116:50
712.66:126:48
812.66:136:47
912.56:146:45
1012.56:156:44
1112.46:166:42
1212.46:176:40
1312.46:176:39
1412.36:186:37
1512.36:196:36
1612.26:206:34
1712.26:216:33
1812.26:226:31
1912.16:236:29
2012.16:236:28
2112.06:246:26
2212.06:256:25
2311.96:266:23
2411.96:276:21
2511.96:286:20
2611.86:296:18
2711.86:296:17
2811.76:306:15
2911.76:316:13
3011.76:326:12

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.26 kWh/m².

For context, solar energy here swings from a low near 2.24 kWh/m² to a high of 5.83 kWh/m² in May across the year — September's 4.26 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.3Bright
24.3Bright
34.3Bright
44.3Bright
54.3Bright
64.3Bright
74.3Bright
84.3Bright
94.3Bright
104.3Bright
114.3Bright
124.3Bright
134.3Bright
144.3Bright
154.3Bright
164.3Bright
174.3Bright
184.2Bright
194.2Bright
204.2Bright
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 Ansan

In seasonPeak

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

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

Ansan's rainy season runs July–August, 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 Ansan?

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

7.3
Sightseeing
1st-best month of the year
5.8
Beach & pool
2nd-best month of the year

September is one of the better times to visit Ansan for general sightseeing.

What to pack for Ansan in September

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

In September, Ansan sees daytime highs around 24°C and nights near 19°C. Worth packing: light clothes. About 7 days see rain.

light clothes

Sea temperature near Ansan in September

The nearest coast averages about 23°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 24°C and coldest in February near 4°C.

It's comfortable for a long swim from Jul 11 to Oct 13 — about 3.1 months when the water holds above 20°C.

0°10°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan6Bracing
Feb4Bracing
Mar5Bracing
Apr8Bracing
May12Bracing
Jun17Cool
Jul21Refreshing
Aug24Refreshing
Sep23Refreshing
Oct20Cool
Nov15Bracing
Dec10Bracing

UV index in Ansan in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Ansan peaks around July 23 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 22 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJul 23UV 8Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May6High
Jun7High
Jul8Very high
Aug8Very high
Sep7High
Oct5Moderate
Nov3Moderate
Dec2Low

Air quality in Ansan 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 Ansan is worst in March — around 160 µg/m³ PM2.5 (very unhealthy), about 2.0× the cleanest month (August, 81 µg/m³).

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

0306090120150180JanFebMarAprMayJunJulAugSepOctNovDecUnhealthyVery unhealthyUnhealthyMar 13158 µg/m³Aug 1282 µg/m³
PM2.5 (µg/m³)Level
Jan145Unhealthy
Feb149Unhealthy
Mar160Very unhealthy
Apr127Unhealthy
May111Unhealthy
Jun98Unhealthy
Jul88Unhealthy
Aug81Unhealthy
Sep110Unhealthy
Oct132Unhealthy
Nov142Unhealthy
Dec133Unhealthy
Location & terrain

Where is Ansan?

Ansan sits at 37.3°N, 126.8°E, 15 m above sea level, in South Korea. The nearest listed city is Anyang-si, 12 km away.

Topography around Ansan

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

Within 3 km, the terrain around Ansan has only modest variations in elevation — a maximum elevation change of 198 m around an average of 24 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 470 m; within 80 km, large variations in elevation — a maximum elevation change of 1,126 m.

The land around Ansan is covered by artificial surfaces (58%) and trees (33%) within 3 km, trees (36%) and artificial surfaces (32%) within 16 km, and trees (39%) and water (27%) within 80 km.

3 km
198 m
16 km
470 m
80 km
1,126 m
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: Anyang-si 12 km · Uiwang 12 km · Gunpo 12 km · Hwaseong-si 13 km · Siheungdong 16 km · Suwon 17 km · Gwangmyeong 18 km · Incheon 18 km

South Korea travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type C / F
220 V · 60 Hz
Prices
≈ 57% of US
price level, 2025
GDP per capita
$36,227
2025
Happiness
6.0 / 10
World Happiness, 2025
Safe drinking water
99%
of population, 2024
Homicide rate
0.5
per 100k, 2023
Road deaths
8.6
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 522
Religion
none 60%Protestant 17%Buddhist 16%Catholic 6%

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 Ansan (37.3236°, 126.8219°, 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).