Charleston weather in September

In September, Charleston sees average daytime highs of 78°F and overnight lows near 58°F, with 2.9 in of rain across 7.2 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 10th-wettest month of the year here.

Highs ease over the month, from about 82°F in the first days to 74°F by the end. The sky is clear or mostly clear about 46% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Charleston's 1st-clearest and 9th-windiest month. For the whole year in context, see Charleston's year-round climate.

Daytime high
78°
4th warmest
Overnight low
58°
9th coldest
Rainfall
2.9 in
7.2 wet days
Daylight
12 h 18 min
5:39 AM – 5:55 PM
Cloud cover
46%
1st clearest
Wind
7 mph
9th windiest
Solar energy
4.73 kWh/m²
Travel score
7.3
out of 10

Charleston is city in and the county seat of Coles County, Illinois, United States.

Density
876/km²
people per km²
Founded
1831

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 82°F in the first days to 74°F by the end.

A typical September day in Charleston reaches about 78°F in the afternoon and slips back to 58°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 88°F. Set against its neighbours, September runs about 5°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18264
28263
38263
48263
58262
68162
78161
88161
98061
108060
118060
127959
137959
147958
157858
167858
177857
187757
197756
207656
217656
227655
237555
247554
257554
267454
277453
287453
297353
307352

How September really feels in Charleston

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
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.

Charleston weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan37° / 22°3.08.93.89.50.0
Feb41° / 25°2.57.83.410.40.3
Mar52° / 34°3.410.51.611.72.7
Apr64° / 45°4.811.80.3135.4
May74° / 56°4.712.7014.16.3
Jun82° / 65°4.211.2014.75.9
Jul85° / 68°3.710.7014.55.4
Aug83° / 65°3.08.5013.66.0
Sep78° / 58°2.97.2012.37.3
Oct65° / 46°3.38.20.1116.2
Nov52° / 36°3.58.30.79.82.8
Dec41° / 27°2.78.92.99.30.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 46% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 37%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16337
26337
36337
46337
56436
66436
76436
86436
96337
106337
116337
126337
136238
146238
156139
166139
176139
186040
196040
206139
216139
226238
236238
246337
256337
266436
276436
286535
296535
306535

Chance of precipitation in September

Any precipitation

Charleston gets around 2.9 in of rain over 7.2 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 24% and peaks near 26% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
126
225
325
425
524
624
724
823
923
1023
1123
1223
1323
1423
1524
1624
1724
1825
1925
2025
2125
2226
2325
2425
2525
2625
2725
2824
2924
3024

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 44% of days. Sticky, muggy-or-worse air turns up on roughly 18% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11920242513
22020232512
32220232410
4232023249
5252123238
6272123227
7292123216
8312223205
9332222195
10342222184
11362222173
12382222163
13392121162
14412121152
15432120142
16442120141
17462019131
18482019131
19501918121
20511917121
21551816110
22561815110
23591714100
24601713100
2562161390
2663161290
2763161290
2866151180
2966151180
3069141070

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over September. Sunrise moves from 5:25 AM to 5:53 AM, and sunset from 6:20 PM to 5:31 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:256:20
212.95:266:18
312.85:276:16
412.85:286:15
512.75:296:13
612.75:306:12
712.75:316:10
812.65:326:08
912.65:336:07
1012.55:346:05
1112.55:356:03
1212.45:366:01
1312.45:376:00
1412.35:375:58
1512.35:385:56
1612.35:395:55
1712.25:405:53
1812.25:415:51
1912.15:425:50
2012.15:435:48
2112.05:445:46
2212.05:455:44
2311.95:465:43
2411.95:475:41
2511.95:485:39
2611.85:495:38
2711.85:505:36
2811.75:515:34
2911.75:525:33
3011.65:535:31

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 1.79 kWh/m² to a high of 6.44 kWh/m² in June across the year — September's 4.73 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.2Bright
35.2Bright
45.2Bright
55.1Bright
65.1Bright
75.0Bright
85.0Bright
95.0Bright
104.9Bright
114.9Bright
124.8Bright
134.8Bright
144.8Bright
154.7Bright
164.7Bright
174.6Bright
184.6Bright
194.5Bright
204.5Bright
214.5Bright
224.5Bright
234.4Bright
244.4Bright
254.3Bright
264.3Bright
274.3Bright
284.2Bright
294.2Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Charleston?

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
6.7
Beach & pool
3rd-best month of the year

September is one of the better times to visit Charleston for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Charleston in September

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

In September, Charleston sees daytime highs around 78°F and nights near 58°F. Worth packing: light clothes and sun protection. About 7 days see rain.

light clothessun protection

UV index in Charleston in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Charleston peaks around July 10 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJul 10UV 9Dec 23UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Charleston 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 Charleston is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateModerateGoodJul 1616 µg/m³Oct 218 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar13Moderate
Apr11Good
May14Moderate
Jun15Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Charleston?

Charleston sits at 39.5°N, 88.2°W, 669 ft above sea level, in United States. The nearest listed city is Mattoon, 11 mi away.

Topography around Charleston

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Charleston.

Within 2 miles, the terrain around Charleston has only modest variations in elevation — a maximum elevation change of 187 ft around an average of 676 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 282 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 456 ft.

The land around Charleston is covered by cropland (38%) and trees (32%) within 2 miles, cropland (68%) and trees (23%) within 10 miles, and cropland (74%) and trees (21%) within 50 miles.

2 miles
187 ft
10 miles
282 ft
50 miles
456 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Mattoon 11 mi · Terre Haute 41 mi · Urbana 42 mi · Champaign 43 mi · Decatur 48 mi · Danville 52 mi · Vincennes 66 mi · Crawfordsville 79 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

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 Charleston (39.4962°, -88.1762°, elevation 669 ft), 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. 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).