The state has high inter annual and seasonal variability's of precipitation. The main cause of this is the strength and geographic placement of Bermuda high. As the high pressure continues its grip over the area, solar radiation increases, which in turn increases the temperature, which then decreases the cloud cover, thereby reducing the probability of substantial precipitation.
Droughts are sometimes alleviated by a tropical cyclone. In 1954, Hurricane Hazel ended an extreme drought in eastern South Carolina, although drought conditions continued in western sections. In 1990, the remnants of Hurricane Klaus and Tropical Storm Marco ended an extreme drought.
Precipitation occurs during periods of drought, however, it is highly localized, inconsequential, and generally evaporates within 24-hours after falling. Periods of insufficient rainfall for crop growth occur during some summers. There is approximately a one in four probability of a drought somewhere in South Carolina at any time (Guttman and Plantico, 1987). Field crops such as corn, cotton, and soybeans are greatly stressed when drought conditions extend over several weeks during the growing season because only 9% of all farms in the state have irrigated acres, as compared to 26% nationwide. However, the state has a similar proportion of irrigated acres when compared to Alabama, North Carolina, and Virginia. Only Florida and Georgia have higher percentages of irrigated land in the Southeast United States (U.S. Department of Commerce, 1993).
Historically, droughts have had severe adverse impacts on the people and economy of South Carolina. Periods of dry weather have occurred in each decade since 1818 (National Water Summary 1988-1989 Hydrologic Events and Floods and Droughts, 1991). The earliest records of drought indicate that some streams in South Carolina went dry in 1818, and fish in smaller streams died from lack of water in 1848. The most damaging droughts in recent history occurred in 1954, 1986, and 1998-2002. Less severe droughts were reported in 1988, 1990, 1993, and 1995. The adverse impacts on the people and economy were made especially clear during the drought of 1998-2002 that impacted agriculture, forestry, tourism, power generation, public water supplies, and fresh water fisheries.
Intense coastal storms normally occur during the fall through early spring. Their affects range from high winds and tides along the beaches to rain and occasional snowfall Upstate. The storm system of January 1, 1987, with its gale force winds and abnormally high tides, caused an estimated $25 million worth of damage to South Carolina beachfront properties.
The lowest pressure ever recorded at Columbia occurred on March 13, 1993 during an intense winter cyclone. The cold weather that accompanied this storm resulted in two deaths, one on the 13th, and one on the 15th. In addition to the cold, it dumped 1.5 feet of snow in the Mountains, flurries in the Lowcountry, and caused an estimated $22 million worth of total damage to the state.
Flooding occurs on several streams in the state each year. A certain amount of control can be effected on the large rivers which have dams. The state can experience riverine flooding any month of the year. However, it is most likely to occur in association with tropical cyclones, because of their typically slow forward motion and abundant moisture.
September 16, 1999: The remnants of Hurricane Floyd dumped up 15"-20" of rain along the coast triggering wide spread flooding along the South Carolina Coast. The heavy rains caused record flooding of the Waccamaw River. Over 1700 homes were damaged in Horry County. Three foot flood waters were reported in the vicinity of Murrell's Inlet. No flood related injuries were reported.
October 10-13, and October 22, 1990: . The former was a result of the remnants of Hurricane Klaus and Tropical Storm Marco moving northwards along a stationary front. This flood caused 4 deaths in Kershaw County, when a dam burst sending water across a road trapping the people in their vehicle. Another death occurred in Spartanburg County, when a toddler drowned in a rain-swollen creek. As a result of the flooding, Aiken, Calhoun, Cherokee, Darlington, Edgefield, Florence, Kershaw, Lee, Orangeburg, Spartenburg, Sumter, and Union counties were declared federal disaster areas.
August 1908: The most extensive flooding in South Carolina history occurred on this date. All the major rivers of the state rose from 9 to 22 feet above flood stage.
Excessive amounts of rain was received in the extreme eastern counties and in all of the northern and western counties. Reporting locations recorded two to four times the normal amount of rainfall, most which fell from the 23rd to the 26th, causing floods in all the streams and rivers of the upper and central portions. The floodwaters rose to greater heights and the floods were more destructive, and the money value of the damage was greater than ever before known, authentic records being available for comparison since 1840.
The greatest twenty-four hour rainfall was 11.65 inches, at Anderson, on the 24th-25th. On the 24th-26th, Anderson had 14.31 inches in 34 hours, at Blairs on the 24th-26th had in 60 hours; at Calhoun Falls on the 23rd-26th, 9.62 inches in 63 hours, at Camden on the 25th-26th, at Catawba on the 23rd-26th, 10.12 inches in 65 hours; at Cheraw on the 24th-26th, 6.52 inches in 62 hours, at Clemson College on the 25th, 2.81 inches in 24 hours, at Conway on the 26th, 2.83 inches in 14 hours, at Greenville on the 23rd-26th, 16.94 inches in 78 hours, at Greenwood on the 24th-26th, 7.06 inches in 60 hours, at Liberty on the 24-25th, 11.12 inches in 24 hours, at Mt Holly in N.C on the 23rd-26th, 11.19 inches in 58 hours, at Pelzer on the 24th-26th, 5.14 inches in 27 hours, at Santee on the 23-25th, 10.83 inches in 58 hours, at Spartanburg on the 24th-26th, 9.33 inches in 72 hours, at Ferguson on the 26th, 2.59 inches in 24 hours; at Winnsboro on the 24th-25th, 7.85 inches in 48 hours, at Winthrop College on the 24th-25th, 7.10 inches in 48 hours.
Thunderstorms occurred on 21 days during the August of 1908. The periods of maximum frequency were the 2d, 5th, 6th, 8th, 16th, 19th, 21st, 23rd-26th, when from five to eleven of the fifteen stations that recorded thunderstorms reported their occurrence.
June 1903: The highest number of people killed by floodwaters in South Carolina occurred on the Pacolet River, a tributary of the Broad River, when 60 to 80 people drowned in a flash flood.