Raleigh, North Carolina, sits in a transitional zone defined by two major climate classification systems. Its location in the southeastern United States places it firmly within the scientific Köppen classification known as Humid Subtropical. For practical purposes like gardening and landscaping, Raleigh’s territory is currently split, or bordering, the United States Department of Agriculture (USDA) Plant Hardiness Zones 7b and 8a. These classifications define the city’s expected weather patterns, agricultural suitability, and infrastructure needs.
The Primary Climate Classification
Raleigh is classified under the Köppen system as Humid Subtropical, designated by the code Cfa. The “C” indicates a temperate climate, meaning the average temperature of the coldest month is above 32°F (0°C). The letter “f” signifies that the region is fully humid, with precipitation distributed relatively evenly year-round and no significant dry season. The final letter, “a,” indicates a hot summer, defined by having at least one month averaging above 71.6°F (22°C). This combination accurately describes the area’s mild winters, hot summers, and consistent annual rainfall.
Essential Gardening Zones
The most practical classification for residents is the USDA Plant Hardiness Zone (PHZ) system, which determines what perennial plants can survive the winter cold. Raleigh historically fell within Zone 7b, representing an average annual extreme minimum temperature between 5°F and 10°F. The 2023 update shifted much of the area into the warmer Zone 8a, which corresponds to average minimum temperatures between 10°F and 15°F. While this shift allows for a broader range of perennial plants, the PHZ map represents a 30-year average, meaning occasional dips below the 10°F threshold remain a risk. For planting annual vegetables, the average last frost date is around April 1st to April 10th, providing a reliable guide for the start of the outdoor growing season.
Typical Seasonal Characteristics
The Humid Subtropical climate gives Raleigh four distinct, moderate seasons. Summers are long and characterized by high heat and pervasive humidity, with average high temperatures ranging from the mid-80s to the mid-90s Fahrenheit. Afternoon thunderstorms are frequent, delivering intense but brief rainfall. Winters are short and mild, with average high temperatures staying in the low 50s and overnight lows often hovering around the freezing mark. While snowfall is infrequent, the area averages about four to six inches of snow annually, usually in light, temporary events.