Climate of the Appalachian Mountains: Four Seasons, High Variability

Classification

Temperate deciduous forest (Köppen Cfb/Cfa)—distinct seasons, ample precipitation, elevation-driven microclimates.

Temperature

• Annual mean: 40–60°F (4–15°C), dropping ~3.5°F per 1,000 ft gain.
• Summer (Jul): 70–85°F (21–29°C) valleys; 60s°F on high peaks.
• Winter (Jan): 20–40°F (-7–4°C) valleys; sub-zero on summits.
• Extremes: -30°F (-34°C) on Mt. Mitchell; 100°F+ in deep valleys.

Precipitation

• Annual: 40–60 in (100–150 cm), up to 80+ in on windward peaks.
• Distribution: Fairly even; summer convective storms, winter orographic snow.
• Snowfall: 20–100+ in, elevation-dependent; persistent cover >3,000 ft.

Humidity & Clouds

• RH 60–80% year-round; summer muggy, winter damp.
• 50–70% cloud cover; frequent fog in valleys & ridges.

Growing Season

120–180 days (valley to summit). Frost-free: late April–early Oct (valleys); June–Sept (high peaks).

Climate Change Impacts

• +1.5–2°F since 1970; longer growing season.
• More intense downpours, less snowpack.
• Species upslope migration; spruce-fir forest contraction.
• Increased pest outbreaks (hemlock woolly adelgid, spongy moth).