South Carolina has a humid subtropical climate (Köppen climate classification Cfa), although high elevation areas in the "Upstate" or "Upcountry" area have less subtropical characteristics than areas on the Atlantic coastline. In the summer, South Carolina is hot and humid with daytime temperatures averaging between 86–93 °F (30–34 °C) in most of the state and overnight lows averaging 70–74 °F (21–23 °C) on the coast and from 66–73 °F (19–23 °C) inland. Winter temperatures are much less uniform in South Carolina. Coastal areas of the state have very mild winters with high temperatures approaching an average of 60 °F (16 °C) and overnight lows in the 40s°F (5–8 °C). Inland, the average January overnight low is around 32 °F (0 °C) in Columbia and temperatures well below freezing in the Upstate. While precipitation is abundant the entire year in almost the entire state, the coast tends to have a slightly wetter summer, while inland, March tends to be the wettest month and winter being the driest season, with November being the driest month. The highest recorded temperature is 111 °F (44 °C) at Camden on June 28, 1954 and the lowest recorded temperature is −19 °F (−28 °C) at Caesars Head on January 21, 1985.

Snowfall in South Carolina is somewhat common in parts of the state, with coastal areas receiving less than an inch (2.5 cm) annually on average. It is not uncommon for areas on the coast (especially the southern coast) to receive no recordable snowfall in a given year. The interior receives a little more snow, although nowhere in the state averages more than 9 inches (22.86 cm) of snow annually. The mountains of extreme northwestern South Carolina tend to have the most substantial snow accumulation. Freezing rain and ice tend to be more common than snow and rain in many areas of the state. Road bridges in South Carolina are commonly marked, "Bridge ices before road."

The state is occasionally affected by tropical cyclones. This is an annual concern during hurricane season, which lasts from June 1 to November 30. The peak time of vulnerability for the southeast Atlantic coast is from early August to early October, during the Cape Verde hurricane season. Two memorable Category 4 hurricanes to hit South Carolina were Hazel (1954) and Hugo (1989). South Carolina averages around 50 days of thunderstorm activity a year. This is less than some of the states further south, and it is slightly less vulnerable to tornadoes than the states which border on the Gulf of Mexico. Some notable tornadoes have struck South Carolina and the state averages around 14 tornadoes annually. Hail is common with many of the thunderstorms in the state as there is often a marked contrast in temperature of warmer ground conditions compared to the cold air aloft.

Cities: Aiken , Anderson , Bear Swamp , Beaufort , Beech Island , Belvedere , Bennettsville , Berea , Brushy Creek , Burton , Camden , Cayce , Charleston , Clemson , Clinton , Columbia , Conway , Cross , Danwood , Darlington , Dentsville , Dillon , Dutch Fork , Easley , Fairmont Mills , Five Forks , Florence , Forest Acres , Fort Mill , Fountain Inn , Gaffney , Gantt , Garden City , Georgetown , Goose Creek , Gramling , Greenville , Greenwood , Greer , Hanahan , Hartsville , Hendersonville , Highland , Hilton Head Island , Homeland Park , Hopkins , Horrell Hill , Irmo , James Island , Johns Island , Ladson , Lake City , Lancaster , Laurel Bay , Laurens , Lexington , Little River , Longs , Lugoff , Macedonia , Marion , Mauldin , Moncks Corner , Mount Pleasant , Myrtle Beach , Newberry , North Augusta , North Charleston , North Myrtle Beach , Oak Grove , Oakway , Orangeburg , Parker , Pauline , Pontiac , Red Bank , Red Hill , Rock Hill , Sans Souci , Seneca , Seven Oaks , Shaw-Horatio , Simpsonville , Socastee , Spartanburg , St. Andrews , St. Helena , Stevens Creek