Mean annual temperature has increased by almost 1°F since the beginning of the 20th century. Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century.
The number of landfalling hurricanes in North Carolina is highly variable from year to year. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate warms.
A large portion of North Carolina’s coastline is extremely vulnerable to projected sea level rise due to its low elevation and subsidence of land in the northern part of the Coastal Plain. By the end of the 21st century, global sea level is projected to rise 1–8 feet, with a likely range of 1–4 feet.
North Carolina has a humid climate with very warm summers and moderately cold winters. The climate exhibits substantial regional variation due to the state’s diverse geographic elements, which include the Appalachian Mountains in the west, the Piedmont Plateau in the central region, and the Coastal Plain to the east. Elevations in the state range from sea level along the Atlantic Coast to over 6,000 feet in the western mountains (the largest elevation range of any state east of the Mississippi River). Average annual temperatures in the state vary more than 20°F from the highest elevations to the lowest points on the coast. Winter temperatures are moderated somewhat by the Appalachian Mountains which partially block cold air coming from the Midwest.
Mean annual temperature has increased by almost 1°F in North Carolina since 1900, less than in northern and western portions of the United States. North Carolina is part of a larger region of the southeastern U.S. that has exhibited little overall warming in surface temperatures over the 20th century. During the first half of the 20th century, many years were warmer than the long-term average, followed by a cool period in the 1960s and 1970s. Since that time, temperatures have steadily increased, with temperatures being consistently above normal since the late 1990s (Figure 1). Average winter temperatures have been above average since 1990, with the last four-year period (2015–2018) as warm as the early 1930s and early 1950s (Figure 2a). Average summer temperatures have been the warmest on record over the last 14 years (Figure 2b). Although North Carolina has not experienced an increase in the frequency of very hot days (days with maximum temperature at or above 95°F; Figure 3a), the last nine years (2010–2018) have seen the largest number of very warm nights (days with minimum temperature at or above 75°F) in the historical record (Figure 4).
Statewide average annual precipitation has ranged from a low of 34.74 inches in 2007 to a high of 68.4 inches in 2018. The driest multiyear periods were in the early 1930s and early 1950s, and the wettest in the late 1900s and late 2010s (Figure 3b). The driest consecutive 5-year interval was 1930–1934, with an average annual precipitation of 44.4 inches, and the wettest was 2014–2018, with an average of 55.1 inches per year. There is no overall trend in annual precipitation. Precipitation totals are generally highest in the summer, with a peak in July. Southwestern North Carolina is one of the wettest locations in the Southeast, receiving more than 90 inches of precipitation annually in a few locations. The number of heavy rain events (days with rainfall of 3 inches or more) was highest in the last four-year period (2015–2018; Figure 3c). There is no overall trend. The state averages around 5 inches of snowfall annually, although the higher elevations of the Appalachian Mountains can receive up to 100 inches. Snow and ice storms have the potential to cause significant damage. Some of these storms are the result of “cold air damming,” which occurs when cold air becomes trapped against the Appalachian Mountains by a layer of less dense warm air above it. A strong cold air damming event took place on February 12–13, 2014, causing a severe winter storm. Large portions of the state received between 5 and 10 inches of snow and some areas received as much as half an inch of freezing rain.
The “Bermuda High,” a semi-permanent high pressure system off the Atlantic Coast, plays an important role in the summer climate of the state. Typically, the Bermuda High draws moisture northward or westward from the Atlantic Ocean and Gulf of Mexico, causing warm and moist summers with frequent thundershowers in the afternoons and evenings. Daily and weekly variations in the positioning of the Bermuda High can have a strong influence on precipitation patterns. When the Bermuda High extends westward into the southeastern United States, warmer and drier than normal weather occurs, which can culminate in heat waves and drought. In 2007, as the result of a strong Bermuda High over the Southeast and a strengthening La Niña, the state experienced its driest year in history. By the end of August, most of the state was in severe drought.
North Carolina’s location along the Atlantic Coast makes the state vulnerable to tropical storms and hurricanes. A storm reaches the state at hurricane intensity about once every three years (Figure 3d). However, storms that reach the state at less than hurricane intensity can also have major impacts. The late 1990s and early 2000s were a notably active period of storms reaching the state at hurricane intensity (Figure 3d). In addition to damaging winds and coastal flooding from storm surges, extreme precipitation from these storms is a great hazard to the state. In 1999, Hurricane Floyd dropped 15–20 inches of rain in the eastern part of the state, which was still recovering from flooding caused by Hurricane Dennis several weeks earlier. Beginning on September 6, 2004, the remnants of Hurricane Frances dropped 6–10 inches of rain across much of western North Carolina over a three-day period. Less than two weeks later, the remnants of Hurricane Ivan struck the same area, dropping 10 inches of rain and causing hundreds of landslides in the mountains. During October 7–9, 2016, Hurricane Matthew dumped torrential rain in eastern North Carolina with many locations receiving more than 10 inches and a few locations in excess of 18 inches, causing major flooding. In September 2018, the most intense rainfall event on record occurred as Hurricane Florence dropped 20–36 inches in eastern North Carolina, causing widespread destruction with losses in excess of $22 billion (in 2019 dollars), more than the combined losses from Floyd and Matthew. In addition to damage from high winds and flooding, hurricane strikes can produce tornadoes. Rainbands associated with Hurricane Frances spawned multiple tornadoes in the central and eastern portions of the state.
Severe thunderstorms are another hazard commonly experienced within the state. These occasionally spawn tornadoes. The largest such outbreak occurred on April 16, 2011, with 30 confirmed tornadoes and 24 deaths.
Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century (Figure 1). Even under a pathway of lower greenhouse gas emissions, average annual temperatures are projected to most likely exceed historical record levels by the middle of the 21st century. However, there is a large range of temperature increases under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records (Figure 1). Future heat waves are likely to be more intense, but cold wave intensity is projected to decrease.
Although there is no historical trend, annual precipitation is projected to increase in North Carolina (Figure 5), primarily in the winter and spring. Naturally occurring droughts are projected to be more intense because higher temperatures will increase the rate of loss of soil moisture during dry periods. Additionally, hurricane-associated storm intensity and rainfall rates are projected to increase as the climate warms.
Increasing temperatures raise concerns regarding sea level rise in coastal areas. Since 1900, global average sea level has risen by about 7–8 inches. It is projected to rise another 1–8 feet, with a likely range of 1–4 feet, by 2100 as a result of both past and future emissions from human activities (Figure 6). Sea level rise has caused an increase in tidal floods associated with nuisance-level impacts. Nuisance floods are events in which water levels exceed the local threshold (set by NOAA’s National Weather Service) for minor impacts. These events can damage infrastructure, cause road closures, and overwhelm storm drains. As sea level has risen along the North Carolina coastline, the number of tidal flood days (all days exceeding the nuisance level threshold) has also increased, with the greatest number occurring in 2016 and 2018 at Wilmington (Figure 7). Large increases in nuisance flooding at Wilmington are projected (Figure 7). A large portion of North Carolina’s coastline is extremely vulnerable to sea level rise due to its low elevation and to geological factors that are causing sinking of the land in the northern part of the state. Sea level rise will present major challenges to North Carolina’s existing coastal water management system and may cause extensive economic damage through losses in property, tourism, and agriculture.