Several factors control the climate. Most important are the state’s location in the northern mid-latitudes, its proximity to both the Atlantic Ocean and the Appalachian Mountains, and elevation.

The state’s position on the eastern coast of a continent is important because land and water heat and cool at different rates. This provides for cooling sea breezes during the summer and warms the immediate coast during the winter. Also, it influences the way pressure and wind systems affect the state. During the summer, South Carolina’s weather is dominated by a maritime tropical air mass known as the Bermuda high. Passing over the Gulf Stream, it brings warm, moist air inland from the ocean. As the air comes inland, it rises and forms localized thunderstorms, resulting in a precipitation maxima (Trewarhta,1981).

The Appalachian Mountains also exert a major influence on the state’s climate in three ways. First, they tend to block many of the cold air masses arriving from the northwest, thus making the winters somewhat milder. Second, the occurrence of downslope winds, which warm the air by compression, cause the areas leeward of the mountains to experience slightly higher temperatures than the surrounding areas. Hence, the proximity of the mountains to the state results in a more temperate climate than otherwise would be experienced. Lastly, the mountains cause a leeside rain shadow, an area of decreased, precipitation across the Midlands, roughly parallel to the fall line (Kronberg, 1959, Landers, 1970, and Purvis et al., 1990).

The state’s annual average temperature varies from the mid-50’s in the Mountains to low-60’s along the coast. During the winter, average temperatures range from the mid-30’s in the Mountains to low-50’s in the Lowcountry. During summer, average temperatures range from the upper 60’s in the Mountains to the mid-70’s in the Lowcountry.