Sumter weather in September

In September, Sumter sees average daytime highs of 84°F and overnight lows near 67°F, with 4.2 in of rain across 10 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 87°F in the first days to 81°F by the end. The sky is clear or mostly clear about 37% of the time in September, and the air most often feels muggy.

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 Sumter's 8th-clearest and 9th-windiest month. For the whole year in context, see Sumter's year-round climate.

Daytime high
84°
4th warmest
Overnight low
67°
9th coldest
Rainfall
4.2 in
10 wet days
Daylight
12 h 12 min
6:09 AM – 6:22 PM
Cloud cover
55%
8th clearest
Wind
7 mph
9th windiest
Solar energy
4.61 kWh/m²
Travel score
5.6
out of 10

Sumter is city in and county seat of Sumter County, South Carolina, United States.

Density
491/km²
people per km²
Founded
1845

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 87°F in the first days to 81°F by the end.

A typical September day in Sumter reaches about 84°F in the afternoon and slips back to 67°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 76°F and 92°F. Set against its neighbours, September runs about 5°F cooler than August and about 9°F warmer than October.

50°60°70°80°90°151015202530
Avg high (°F)Avg low (°F)
18771
28770
38770
48770
58770
68669
78669
88669
98669
108568
118568
128568
138568
148567
158467
168467
178467
188366
198366
208366
218365
228265
238265
248265
258264
268164
278164
288163
298063
308062

How September really feels in Sumter

Once humidity and wind are folded in, September averages 4 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
4
heat index over the day's high
Days feeling ≤ 32°F
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.

Sumter weather by month

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

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan56° / 37°3.58.90.5104.1
Feb60° / 40°3.38.60.310.74.9
Mar67° / 46°3.49.40.111.76.4
Apr76° / 54°3.48012.87.2
May82° / 63°3.19.5013.76.2
Jun88° / 71°4.213.2014.24.1
Jul91° / 74°4.715.50143.2
Aug89° / 73°4.714.5013.33.7
Sep84° / 67°4.210012.25.6
Oct75° / 56°3.37.6011.17.4
Nov66° / 45°2.87.2010.26.6
Dec59° / 40°3.78.60.19.84.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% 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 (%)
15248
25248
35248
45347
55347
65446
75347
85446
95446
105545
115446
125545
135545
145446
155446
165446
175347
185446
195347
205446
215347
225347
235545
245545
255545
265644
275644
285644
295644
305743

Chance of precipitation in September

Any precipitation

Sumter gets around 4.2 in of rain over 10 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 33% and peaks near 40% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
140
239
339
438
537
637
736
835
935
1034
1134
1233
1333
1433
1532
1632
1732
1832
1932
2032
2131
2231
2331
2430
2530
2629
2729
2828
2928
3028

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the muggy band about 30% of days. Sticky, muggy-or-worse air turns up on roughly 57% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1271529452
2371529432
3381629422
4481629412
5491729391
6591829381
7591929371
86101929351
96102029341
107102030321
118112030311
129112130290
139112130280
1410112130270
1511122130260
1611122130250
1712122130240
1813132131230
1914132131220
2014132031210
2115132031200
2216132031190
2318142031180
2419141931170
2520151930160
2621151929150
2722161929140
2823171928140
2924171927130
3025182026120

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm

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 5:59 AM to 6:20 AM, and sunset from 6:43 PM to 6:02 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:596:43
212.76:006:42
312.76:006:41
412.66:016:39
512.66:026:38
612.66:026:36
712.56:036:35
812.56:046:33
912.56:056:32
1012.46:056:31
1112.46:066:29
1212.46:076:28
1312.36:076:26
1412.36:086:25
1512.26:096:23
1612.26:096:22
1712.26:106:20
1812.16:116:19
1912.16:126:18
2012.16:126:16
2112.06:136:15
2212.06:146:13
2312.06:146:12
2411.96:156:10
2511.96:166:09
2611.86:176:07
2711.86:176:06
2811.86:186:05
2911.76:196:03
3011.76:206:02

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.61 kWh/m².

For context, solar energy here swings from a low near 2.42 kWh/m² to a high of 6.2 kWh/m² in June across the year — September's 4.61 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
35.0Bright
45.0Bright
55.0Bright
64.9Bright
74.9Bright
84.9Bright
94.8Bright
104.8Bright
114.8Bright
124.7Bright
134.7Bright
144.7Bright
154.6Bright
164.6Bright
174.6Bright
184.5Bright
194.5Bright
204.5Bright
214.4Bright
224.4Bright
234.4Bright
244.3Bright
254.3Bright
264.3Bright
274.3Bright
284.2Bright
294.2Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Sumter?

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

5.6
Sightseeing
6th-best month of the year
6.8
Beach & pool
2nd-best month of the year

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

What to pack for Sumter in September

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

In September, Sumter sees daytime highs around 84°F and nights near 67°F. Pack light clothes. Worth having: rain gear and sun protection. About 10 days see rain.

light clothesrain gearsun protection

UV index in Sumter 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 Sumter peaks around July 13 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 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 highHighModerateJul 13UV 9Dec 20UV 3
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr7High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7Very high
Oct5Moderate
Nov4Moderate
Dec3Moderate

Air quality in Sumter 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 Sumter is worst in March — around 18 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1518 µg/m³Dec 178 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb11Good
Mar18Moderate
Apr13Moderate
May13Moderate
Jun17Moderate
Jul18Moderate
Aug16Moderate
Sep12Good
Oct9Good
Nov8Good
Dec8Good
Location & terrain

Where is Sumter?

Sumter sits at 33.9°N, 80.3°W, 171 ft above sea level, in United States. The nearest listed city is Florence, 38 mi away.

Topography around Sumter

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

Within 2 miles, the terrain around Sumter has only modest variations in elevation — a maximum elevation change of 98 ft around an average of 171 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 305 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,079 ft.

The land around Sumter is covered by trees (63%) and artificial surfaces (25%) within 2 miles, trees (64%) within 10 miles, and trees (75%) within 50 miles.

2 miles
98 ft
10 miles
305 ft
50 miles
1,079 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Florence 38 mi · Columbia 40 mi · West Columbia 42 mi · Saint Andrews 44 mi · Seven Oaks 47 mi · Lexington 52 mi · Summerville 63 mi · Goose Creek 67 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 Sumter (33.9204°, -80.3415°, elevation 171 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).