Weather Conditions on Mount Everest

Mount Everest (8,848.86 m) endures some of Earth’s most extreme weather. Conditions vary drastically by season and altitude.

Temperature

• Average: -19°C (-2°F) at summit.
• Extremes: -62.2°C (-80°F) recorded (Jan 1985); +19°C (67°F) in sun at lower slopes (Aug 2005).
• Lapse Rate: ~6.4°C per 1,000 m gain.

Wind

• Average: 25 km/h (16 mph).
• Extreme: 285 km/h (177 mph) recorded (Mar 1983).
• Seasonality: Strongest in winter (jet stream overhead); calmest in May and September (pre- and post-monsoon).

Precipitation

• Annual: ~1,750 mm (69 in) water equivalent.
• Form: Mostly snow; heavy events can deposit 1.2 m (4 ft) in a day.
• Monsoon: June–September brings most moisture from Bay of Bengal.

Humidity

• Average: 40% (very dry air at altitude).
• Seasonal: Lowest in winter, highest in summer monsoon.

Weather Patterns

• Jet Stream: Persistent westerly winds >100 km/h at summit level; shifts north in summer, allowing brief climbing windows.
• Cyclones/Anticyclones: Bay of Bengal cyclones can bring heavy snow; high-pressure systems bring clear, frigid conditions.

Climate Change Impacts

• Summit warming ~2°C since 1950s.
• Glacier retreat, ice loss, increased rockfall.
• Unpredictable weather windows, higher avalanche risk.

Climbers face extreme cold, hurricane-force winds, hypoxia, and sudden storms. Forecasting and timing are critical for survival.