Why Does Temperature Drop with Altitude?
As elevation increases, atmospheric temperature decreases due to adiabatic expansion. The physical mechanisms and mathematical lapse rates of this atmospheric cooling can be modeled with high precision.
Within the troposphere (0–36,000 ft), rising air expands under decreasing pressure, cooling at the standard environmental lapse rate of approximately 6.5°C per 1,000 m (3.56°F per 1,000 ft). This gradient is known as the environmental lapse rate and averages 6.5°C per 1,000 m (approx. 3.56°F per 1,000 ft) according to the International Standard Atmosphere (ISA). Ambient sea-level air at 77°F (25°C) drops to roughly 54°F (12°C) at 6,500 ft (2,000 m) and 19°F (−7°C) at 16,400 ft (5,000 m).
Atmospheric pressure follows the standard barometric formula: P = 1013.25 × (1 − 0.0000225577 × h)^5.25588. Reduced atmospheric pressure also lowers the boiling temperature of water: boiling point drops from 212°F (100°C) at sea level to approximately 180°F (82°C) on high mountain peaks like Mount Rainier (14,411 ft / 4,392 m). Food takes longer to cook at altitude and requires pressure cooking.
This calculator determines temperature, pressure, water boiling point, and oxygen levels simultaneously for mountaineering and meteorological planning.