What is the standard temperature at 20,000 feet?

The standard temperature at 20,000 feet is indeed -25°C. This value is derived from the International Standard Atmosphere (ISA) model, which defines standard temperature and pressure conditions at various altitudes. According to the ISA, the temperature decreases at a rate of about 6.5°C for every 1,000 meters (or approximately 3.6°F per 1,000 feet) of altitude gained.

At sea level, the standard temperature is typically 15°C. As we ascend to 20,000 feet, the temperature drops significantly. By calculating the decrease over that altitude, you would find:

1. The altitude of 20,000 feet is approximately 6,096 meters.

2. Using the lapse rate, the temperature reduction would be about 6.5°C per 1,000 meters multiplied by the number of thousands of meters (approximately 6.096). This gives us about a reduction of 39.5°C.

3. Subtracting this reduction from the sea level standard temperature of 15°C results in a temperature at 20,000 feet of roughly -24.5°C, which rounds to -25°C.

This calculation aligns with the accepted aviation standards, confirming that