Definition
A temperature scale on which, at standard sea-level pressure, water freezes at 32° and boils at 212°, giving a 180-degree span between those two reference points. It is the temperature scale most commonly used in U.S. aviation weather reporting, performance charts, and cockpit displays.
Plain English
A way of measuring how hot or cold something is, where freezing water is 32 and boiling water is 212. It is the temperature scale you grew up with in the United States.
Context Anchor
Seen in some FAA training material, aircraft manuals, cockpit displays, and maintenance or operating notes when temperature is given in U.S. customary units.
Derivation
Named after Daniel Gabriel Fahrenheit, the 18th-century German physicist who designed the scale and built the first reliable mercury thermometer. Knowing it is a person’s name explains why the scale’s reference points (32 and 212) look arbitrary — they came from his original calibration choices, not from a clean decimal system like Celsius.
Why Pilots Care
Temperature readings affect air density, which changes stall speed, engine power output, and required runway length.
Intuition Check
Do not treat Fahrenheit and Celsius as interchangeable. The same actual temperature has different numbers on the two scales.
Example Sentence 1
The outside air temperature gauge read 85 °F, so the pilot converted it to about 29 °C before checking the takeoff performance chart.
Example Sentence 2
Before takeoff the pilot checked that the outside air temperature was still below 80°F to ensure adequate climb performance.