Climate of North Carolina

A downed tree in Asheville, North Carolina caused by snowfall from the 1993 Storm of the Century

Snow in North Carolina is seen on a regular basis in the mountains. North Carolina averages 5 inches (130 mm) of snow a year. However, this also varies greatly across the state. Along the coast, most areas register less than 2 inches (51 mm) per year while the state capital, Raleigh averages 7.5 inches (190 mm). Farther west in the Piedmont-Triad, the average grows to approximately 9 inches (230 mm). The Charlotte area averages approximately 6.5 inches (170 mm). The town of Boone, North Carolina, located at an elevation of 3,333 feet in the northwestern part of the state, averages approximately 35 inches of snow a year. The mountains in the west act as a barrier, preventing most snowstorms from entering the Piedmont. When snow does make it past the mountains, it is usually light and is seldom on the ground for more than two or three days. However, several storms have dropped 18 inches (460 mm) or more of snow within normally warm areas. The 1993 Storm of the Century that lasted from March 11 to March 15 affected locales from Canada to Central America, and brought a significant amount of snow to North Carolina. Newfound Gap received more than 36 inches (0.91 m) of snow with drifts more than 5 feet (1.5 m), while Mount Mitchell measured over 4 feet (1.2 m) of snow with drifts to 14 feet (4.3 m).[12] Most of the northwestern part of the state received somewhere between 2 feet (0.61 m) an 3 feet (0.91 m) of snow.

Another significant snowfall hit the Raleigh area in January 2000 when more than 20 inches (510 mm) of snow fell.[13] There was also a heavy snowfall totaling 18 inches (460 mm) that hit the Wilmington area on December 22–23, 1989. This storm affected only the Southeastern US coast, as far south as Savannah, GA, with little to no snow measured west of I-95. Most big snows that impact areas east of the mountains come from extratropical cyclones which approach from the south across Georgia and South Carolina and move off the coast of North or South Carolina. These storms typically throw Gulf or Atlantic moisture over cold Arctic air at ground level, usually propelled southward from Arctic high pressure over the Northeastern or New England states. If the storms track sufficiently far to the east, snow will be limited to the eastern part of the state (as with the December 22–23, 1989 storm). If the cyclones travel close to the coast, warm air will get pulled into eastern North Carolina due to increasing flow off the milder Atlantic Ocean, bringing a rain/snow line well inland with heavy snow restricted to the Piedmont, foothills and mountains, as with the January 22, 1987 storm. If the storm tracks inland into eastern North Carolina, the rain/snow line ranges between Raleigh and Greensboro.[14]

Heavy rains accompany tropical cyclones and their remnants which move northeast from the Gulf of Mexico coastline, as well as inland from the western subtropical Atlantic ocean. Over the past 30 years, the wettest tropical cyclone to strike the coastal plain was Hurricane Floyd of September 1999, which dropped over 24 inches (610 mm) of rainfall north of Southport. Unlike Hazel and Fran, the main force of destruction was from precipitation. Before Hurricane Floyd reached North Carolina, the state had already received large amounts of rain from Hurricane Dennis less than two weeks before Floyd. This saturated much of the Eastern North Carolina soil and allowed heavy rains from Hurricane Floyd to turn into floods. Over 35 people died from Floyd.[15] In the mountains, Hurricane Frances of September 2004 was nearly as wet, bringing over 23 inches (580 mm) of rainfall to Mount Mitchell.[16]

Tornado activity in the United States

In winter, North Carolina is somewhat protected by the Appalachian Mountains to the west. Cold fronts from Canada are typically reduced in intensity by the mountains. However, occasionally cold air can move from the north or northeast, east of the Appalachian Mountains, from Arctic high pressure systems that settle over the Northeastern or New England states. Other polar and Arctic outbreaks can cross the mountains and force temperatures to drop to about 12 °F (−11 °C) in central North Carolina. Still, temperatures below zero degrees Fahrenheit are extremely rare outside of the mountains. The coldest ever recorded temperature in North Carolina was −34 °F (−37 °C) on January 21, 1985, at Mount Mitchell. The winter temperatures on the coast are milder due to the warming influence of the Atlantic Ocean and the Gulf Stream.[23] The average ocean temperature in Southport in January is still higher than the average ocean temperature in Maine during July.[23] Snow is common in the mountains, although many ski resorts use snowmaking equipment to make sure there is always snow on their land.[23] North Carolina's relative humidity is highest in the winter.[23]

Tornadoes are most likely in the spring. Major tornado outbreaks affected parts of eastern North Carolina on March 28, 1984, and April 16, 2011. The month of May experiences the greatest rise in temperatures. During the spring, there are warm days and cool nights in the Piedmont. Temperatures are somewhat cooler in the mountains and warmer, particularly at night, near the coast.[23] North Carolina's humidity is lowest in the spring.[23]

Harris Lake in Highlands, North Carolina during fall

North Carolina experiences high summer temperatures. Sometimes, cool, dry air from the north will invade North Carolina for brief periods of time, with temperatures quickly rebounding.[24] It remains colder at high elevations, with the average summer temperature in Mount Mitchell lying at 68 °F (20 °C). Morning temperatures are on average 20 °F (12 °C) lower than afternoon temperatures, except along the Atlantic Coast.[23] The largest economic loss from severe weather in North Carolina is due to severe thunderstorms in the summer, although they usually only hit small areas.[23] Tropical cyclones can impact the state during the summer as well. Fogs are also frequent in the summer.

Fall is the most rapidly changing season temperature wise, especially in October and November.[23] Tropical cyclones remain a threat until late in the season. The Appalachian Mountains are frequently visited at this time of year, due to the leaves changing color in the trees.[23]

During El Niño events, winter and early spring temperatures are cooler than average with above average precipitation in the central and eastern parts of the state and drier weather in the western part. La Niña usually brings warmer than average temperatures with above average precipitation in the western part of the state while the central and coastal regions stay drier than average.