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Sumter, South Carolina climate

Cfa Humid subtropical

Sumter has a seasonal mild-temperate climate (Humid subtropical, Köppen Cfa). The hottest month is July with an average daily high near 90°F, while the coldest is January averaging around 33°F at night. Precipitation is fairly even year-round, totalling about 49 inches.

☀️ Summers

Hot

Highs near 90°F in July.

About 56 days a year above 90 °F

❄️ Winters

Chilly

Lows near 33°F in January.

About 55 freezing nights a year

🌧️ Rain

Wet

About 49 in of rain a year.

Wettest in July

⛅ Sky & trend

Partly cloudy

A roughly even mix of sun and cloud.

−1.1 °F vs 50 years ago

Temperature & precipitation

Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figures

Clear vs cloudy days

Share of days each month that are clear, partly cloudy or cloudy · 1991–2020 · hover a month for the day counts

Sumter climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	55	59	66	75	81	87	90	89	83	74	65	57
Avg temp (°F)	44	47	54	62	70	77	80	79	73	63	52	46
Avg low (°F)	33	35	41	50	58	66	70	68	63	51	40	35
Precipitation (in)	3.8	3.5	3.7	3.4	3.8	5.1	5.8	4.9	4.4	3.9	2.9	3.8
Snowfall (in)	0.3	—	—	—	—	—	—	—	—	—	—	—

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	55	59	66	75	81	87
Avg temp (°F)	44	47	54	62	70	77
Avg low (°F)	33	35	41	50	58	66
Precipitation (in)	3.8	3.5	3.7	3.4	3.8	5.1
Snowfall (in)	0.3	—	—	—	—	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	90	89	83	74	65	57
Avg temp (°F)	80	79	73	63	52	46
Avg low (°F)	70	68	63	51	40	35
Precipitation (in)	5.8	4.9	4.4	3.9	2.9	3.8
Snowfall (in)	—	—	—	—	—	—

How often — frequency of weather events

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	11	9	9	8	9	12	11	11	9	8	8	11
Days with high ≥ 90°F (days)	—	—	—	0.5	4	12	19	14	6	0.3	—	—
Days with low ≤ 32°F (days)	16	11	7	0.4	—	—	—	—	—	0.4	6	14
Days with snowfall ≥ 1 in (days)	0.1	—	—	—	—	—	—	—	—	—	—	—

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	11	9	9	8	9	12
Days with high ≥ 90°F (days)	—	—	—	0.5	4	12
Days with low ≤ 32°F (days)	16	11	7	0.4	—	—
Days with snowfall ≥ 1 in (days)	0.1	—	—	—	—	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	11	11	9	8	8	11
Days with high ≥ 90°F (days)	19	14	6	0.3	—	—
Days with low ≤ 32°F (days)	—	—	—	0.4	6	14
Days with snowfall ≥ 1 in (days)	—	—	—	—	—	—

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	56	59	54	51	52	56	56	57	51	44	47	55
Clear days (≤ 30% cloud)	9	7	9	10	9	7	6	6	10	14	12	9
Partly cloudy days (30–70%)	10	9	10	10	11	12	14	13	11	8	9	9
Cloudy days (≥ 70%)	13	12	12	10	11	11	11	12	10	10	9	12
Relative humidity (%)	81	81	79	75	70	70	69	71	72	72	73	79
Wind speed (mph)	5.3	5.6	5.9	5.9	5.2	4.6	4.5	4.2	4.9	4.9	4.9	5.0

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	56	59	54	51	52	56
Clear days (≤ 30% cloud)	9	7	9	10	9	7
Partly cloudy days (30–70%)	10	9	10	10	11	12
Cloudy days (≥ 70%)	13	12	12	10	11	11
Relative humidity (%)	81	81	79	75	70	70
Wind speed (mph)	5.3	5.6	5.9	5.9	5.2	4.6

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	56	57	51	44	47	55
Clear days (≤ 30% cloud)	6	6	10	14	12	9
Partly cloudy days (30–70%)	14	13	11	8	9	9
Cloudy days (≥ 70%)	11	12	10	10	9	12
Relative humidity (%)	69	71	72	72	73	79
Wind speed (mph)	4.5	4.2	4.9	4.9	4.9	5.0

Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Sumter (NOAA GHCN station USC00388440), about 2 km from the city centre.

Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.

How we build these numbers →