Mount Everest Temperature: Cold, Colder, Coldest

Everest doesn't do "warm." The summit (8,848.86 m / 29,031.7 ft) lives in the jet stream, where physiology fails and equipment defines survival.

Summit Temperatures

• Average annual: −36°C (−33°F)
• Winter (Dec–Feb): −40 to −60°C (−40 to −76°F). Wind chill: −70°C+.
• Spring (Apr–May): −25 to −35°C. Primary climbing window.
• Summer (Jun–Aug): −15 to −25°C. Monsoon clouds, snow, avalanche risk.
• Autumn (Sep–Nov): −20 to −35°C. Post-monsoon window (shorter).
• Record low: −60°C (−76°F) estimated. Wind chill unmeasurable.
• Never above freezing at summit. 0°C is theoretical ceiling.

Base Camp (5,364m / 17,598 ft)

• Day: −5 to +10°C (sun on tent = warmer)
• Night: −15 to −5°C
• Comfortable in sun with proper gear. The "warm" end of the mountain.

Why So Cold?

• Lapse rate: ~6.5°C/km. Sea level 15°C → summit −43°C (theoretical).
• Jet stream: 100–300 km/h winds strip boundary layer, amplify convective cooling.
• Albedo: Snow reflects 80–90% solar radiation.
• Thin air: Low heat capacity, low thermal conduction.

Physiological Impact

Exposed skin freezes in minutes. Corneas freeze. Lungs hemorrhage (high-altitude pulmonary edema). Fingers/toes necrose. Every system fails. Climbers survive in microclimates (tents, down suits, supplemental O₂) — not the mountain's climate.

Everest's cold isn't weather. It's the absence of heat capacity at the top of the troposphere.