International Standard Atmosphere
- Earth's long-term average global temperature is 59°F (15°C)
- The average decrease in temperature with altitude through the lowest 11 km (approx. 36,000 ft) is roughly 6.5°C per 1000 m (3.6°F or 2°C/1000 ft).
Aeronautical Information Manual
Shein, Karsten, "Common Sense and Winter Flying," Professional Pilot, Nov 2011