Mount Everest Climate: The Death Zone's Relentless Extremes
Weather at the Roof of the World
Everest (8,848.86 m) sits in the jet stream for much of the year. Its climate is defined by extreme cold, hurricane-force winds, intense radiation, and hypoxia.
Summit Conditions (Typical)
- Temperature: Annual avg –36°C; Jan avg –57°C; July avg –19°C. Record: –60°C.
- Wind: 100–200+ km/h (jet stream); calm windows rare.
- Pressure: ~33.7 kPa (⅓ sea level) → 6.9% O₂ per breath.
- Solar radiation: UV index 10+; albedo from snow → severe burns, snow blindness.
- Precipitation: Mostly wind-blown snow; low accumulation at summit.
Seasonal Windows
| Season | Months | Characteristics | Climbing |
|---|
| Pre-monsoon | Apr–May | Jet shifts north; brief calm periods; cold | Primary window (90% of summits) |
| Monsoon | Jun–Sep | Heavy snow, avalanches, zero visibility | Almost none |
| Post-monsoon | Sep–Oct | Stable but colder; shorter days | Secondary window |
| Winter | Nov–Mar | Extreme cold, jet stream parked overhead | Rare, elite only |
Altitude Physiology
- Acute Mountain Sickness (AMS): Headache, nausea, insomnia >2,500 m.
- HAPE/HACE: Pulmonary/cerebral edema – fatal without descent.
- Acclimatization: 6–8 weeks of rotations (Base Camp 5,364 m → C1 6,065 m → C2 6,500 m → C3 7,200 m → C4 7,920 m).
- Supplemental O₂: Standard >7,000 m (2–4 L/min); “no-O₂” ascents <3% of summits.
Climate Change Impacts
- Glacier loss: Khumbu Glacier thinning 1 m/yr; ice cliffs collapsing.
- Route instability: Khumbu Icefall more dynamic; crevasse shifts.
- Snow line rise: Less snow cover → more exposed ice/rock → higher objective hazard.
- Weather predictability decreasing – narrower, less reliable windows.
Bottom Line
Everest’s climate is not just “cold”—it’s a multivariate physiological assault. Success requires meteorological literacy, logistical precision, and physiological margin. The mountain decides.
Wanderlust World