North Carolina has a humid, subtropical climate. Winters are short and mild, while summers are usually very sultry; spring and fall are distinct and refreshing periods of transition. In most of North Carolina, temperatures rarely go above 100°F (38°C) or fall below 10°F (–12°C), but differences in altitude and proximity to the ocean create significant local variations. Average January temperatures range from 36°F (21°C) to 48°F (9°C), with an average daily maximum January temperature of 51°F (11°C) and minimum of 29°F (–2°C). Average July temperatures range from 68°F (20°C) to 80°F (27°C), with an average daily high of 87°F (31°C) and a low of 66°F (19°C). The coldest temperature ever recorded in North Carolina was –34°F (–37°C), registered on 21 January 1985 on Mt. Mitchell; the hottest, 110°F (43°C), occurred on 21 August 1983 at Fayetteville.
In the southwestern section of the Blue Ridge, moist southerly winds rising over the mountains drop more than 80 in (203 cm) of precipitation per year, making this region the wettest in the eastern states; the other side of the mountains receives less than half that amount. Average annual precipitation at Charlotte (1971–2000) was 43.5 in (110.5 cm). The piedmont gets between 44 and 48 in (112 to 122 cm) of precipitation per year, while 44 to 56 in (112 to 142 cm) annually fall on the coastal plain. Average winter snowfalls vary from 50 in (127 cm) on Mt. Mitchell to only a trace amount at Cape Hatteras. In the summer, North Carolina weather responds to the Bermuda High, a pressure system centered in the mid-Atlantic. Winds from the southwest bring masses of hot humid air over the state; anticyclones connected with this system frequently lead to upper-level thermal inversions, producing a stagnant air mass that cannot disperse pollutants until cooler, drier air from Canada moves in. During late summer and early autumn, the eastern region is vulnerable to high winds and flooding from hurricanes. Hurricane Diana struck the Carolina coast in September 1984, causing $36 million in damage. A series of tornadoes in March of that year killed 61 people, injured over 1,000, and caused damage exceeding $120 million. Hurricanes Hugo (1989) and Fran (1996) caused major damage.