Like much of the southeastern United States, Raleigh has a humid subtropical climate (Köppen Cfa), with four distinct seasons. Winters are short and generally cool, with a normal January daily mean temperature of 41.0 °F (5.0 °C). On average, there are 69 nights per year that drop to or below freezing, and only 2.7 days that fail to rise above freezing. Raleigh receives an average annual rainfall of 43.34 inches (110.1 cm). Annual and monthly (temperature and) precipitation data are in chart below. April is the driest month, with an average of 2.92 inches (74.2 mm) of precipitation. Precipitation is well distributed around the year, with a slight maximum between July and September; on average, July is the wettest month, owing to generally frequent, sometimes heavy, showers and thunderstorms. Summers are hot and humid, with a normal July daily mean temperature of 80.0 °F (26.7 °C). There are 48 days per year with highs at or above 90 °F (32 °C). Autumn is similar to spring overall but has fewer days of rainfall, but greater potential for extremely heavy rainfall in a one/two day period, owing to occasional threat from tropical weather systems (hurricanes and tropical storms) packing torrential rainfall. In September 1999, Raleigh recorded its wettest month ever, with over 21 inches of rain, due to torrential rainfall from tropical weather systems, most notably Hurricane Floyd on September 15–16. Extremes in temperature have ranged from −9 °F (−23 °C) on January 21, 1985 up to 105 °F (41 °C), most recently on July 8, 2012.
Raleigh receives an average of 6.0 inches (15.2 cm) of snow in winter. Freezing rain and sleet also occur most winters, and occasionally the area experiences a major damaging ice storm. On January 24–25, 2000, Raleigh received its greatest snowfall from a single storm – 20.3 inches (52 cm) – the Winter Storm of January 2000. Storms of this magnitude are generally the result of cold air damming that affects the city due to its proximity to the Appalachian Mountains. Winter storms have caused traffic problems in the past as well.
The region also experiences occasional periods of drought, during which the city sometimes has restricted water use by residents. During the late summer and early fall, Raleigh can experience hurricanes. In 1996, Hurricane Fran caused severe damage in the Raleigh area, mostly from falling trees. Hurricanes Dennis and Floyd in September 1999 were primary contributors to that month’s extreme rainfall of over 21 inches. The most recent hurricane to have a considerable effect on the area was Hurricane Florence in 2018. Tornadoes also have on occasion affected the city of Raleigh, most notably the November 28, 1988 tornado which occurred in the early morning hours and rated an F4 on the Fujita Tornado Scale and affected northwestern portions of the city. There also was the April 16, 2011 EF3 tornado, which affected portions of downtown and northeast Raleigh and the suburb of Holly Springs.
Summary for Raleigh, NC, USA The climate of Raleigh, NC is classified as humid subtropical using Koppen Climate Classification (KCC). Summers are hot and humid with thunderstorms occurring 45 days a year during an average 4 month period. Winters are generally mild to warm with 18 days of snowfall annually. Rainfall averages 50 inches per year. Raleigh is sunny about 61% of the time in summer and 58% of the time in winter. Hurricanes are infrequent but have caused extensive damage from flooding or wind in September 4 out of the last 115 years. Other significant weather events that may occur include ice storms which can cause tree damage due to heavy weight of ice accretion (average 1 event every 4 years), and tornadoes (3 events in last 115 years). Temperatures have risen about 2°F over the past century. It is very likely that Raleigh will continue to warm with future climate change, however there might be a chance that winters will become slightly cooler as well. The trend for strong precipitation events has increased – extremely heavy rainfall may become more frequent leading to possible flooding problems.