South Carolina has a humid subtropical climate, a designation shared by many regions on the eastern side of continents in the mid-latitudes. This results in abundant rainfall, hot, humid summers, and mild winters. The state experiences four distinct seasons, though their characteristics vary significantly across its geography. Calculating the average temperature is complex due to the state’s varied topography and the Atlantic Ocean, which constantly moderates the climate near the coast.
Statewide Annual and Seasonal Temperature Benchmarks
The overall average annual temperature for South Carolina is approximately \(62.4^\circ\text{F}\). This figure places it among the warmer states in the nation and provides a useful benchmark for the general warmth of the region.
The summer season (June through August) has a statewide average temperature of about \(79.4^\circ\text{F}\). Daytime high temperatures across most of the state hover near \(90^\circ\text{F}\), with overnight lows settling around \(70^\circ\text{F}\). This consistent heat is often accompanied by high humidity.
The winter season (December through February) has a much lower average temperature of \(46.1^\circ\text{F}\). Coastal areas experience milder conditions, with average highs reaching \(60^\circ\text{F}\) and lows around \(38^\circ\text{F}\). Further inland in the Piedmont, temperatures average closer to \(50^\circ\text{F}\) during the day and can drop to \(32^\circ\text{F}\) at night.
The transitional seasons of spring and fall provide comfortable temperatures. Spring, particularly in April, sees daytime temperatures ranging from \(64^\circ\text{F}\) to \(75^\circ\text{F}\), while overnight lows range from \(42^\circ\text{F}\) to \(55^\circ\text{F}\). Autumn maintains pleasant conditions, with average temperatures remaining in the \(70^\circ\text{F}\) and high \(60^\circ\text{F}\) range well into November.
How Geography Shapes Regional Temperatures
South Carolina’s temperatures are not uniform across its boundaries, forming a clear gradient shaped by three major geographic regions: the Coastal Plain, the Midlands, and the Upstate. The largest influence is the Atlantic Ocean, which provides a strong moderating effect on the climate of the Coastal Plain and the Lowcountry. Because water heats and cools more slowly than land, coastal cities like Charleston maintain minimum temperatures that are consistently warmer than inland locations during the winter.
The Coastal Plain benefits from this maritime influence, resulting in annual average temperatures in the low \(60^\circ\text{F}\) range. While summer high temperatures are comparable to those inland, the coastal region frequently experiences sea breezes. These breezes provide a slight cooling effect, particularly in the late afternoon, though humidity remains high.
Moving northwest into the Upstate and Piedmont regions, the climate becomes less subtropical and more continental. Elevation gradually increases, culminating in the mountain areas of the extreme northwest. This higher elevation and distance from the ocean result in greater temperature variation.
The Upstate, including cities like Greenville and Spartanburg, experiences a lower average annual temperature, often falling into the mid-\(50^\circ\text{F}\) range. Winter lows are significantly colder, with more frequent freezes and occasional snowfall, due to the lack of the ocean’s thermal inertia. The Upstate also tends to have a slightly shorter growing season and more pronounced temperature swings throughout the year.
Analyzing Temperature Extremes
While average temperatures define the typical climate, South Carolina also includes significant temperature extremes. The state’s official all-time record high temperature is \(113^\circ\text{F}\). This extreme heat was recorded in Columbia, the state’s capital, on June 29, 2012, during a severe heatwave. Such high temperatures highlight the potential for dangerous heat conditions, particularly in the inland Midlands region.
On the other end of the spectrum, the state’s record low temperature is \(-19^\circ\text{F}\). This record was set in the mountainous Upstate region at Caesars Head on January 21, 1985. Despite generally mild winters, powerful cold air masses can penetrate the state and cause severe freezing conditions, especially at higher elevations.
Prolonged heatwaves, where temperatures exceed \(100^\circ\text{F}\), are an annual risk compounded by high humidity. For example, Charleston once experienced a record of 74 consecutive days with high temperatures above \(90^\circ\text{F}\). Severe winter freezes, though less frequent than heatwaves, still occur and can lead to ice storms or rare inland snowfall events, impacting infrastructure and agriculture.