Definition
A unit of temperature measurement on the Fahrenheit scale, in which water freezes at 32 °F and boils at 212 °F at standard sea-level pressure. Commonly used in U.S. aviation for reporting outside air temperature, carburetor air temperature, and cylinder head temperature.
Plain English
A way of measuring how hot or cold something is, using the temperature scale most people in the U.S. grew up with — where freezing water is 32 and boiling water is 212.
Context Anchor
Seen in carburetor icing charts, weather information, and temperature limits in U.S. aviation materials.
Derivation
Named after Daniel Gabriel Fahrenheit, the German physicist who developed the scale in 1724. Knowing it is a person's name (not a description of anything physical) helps explain why the numbers don't line up neatly with freezing and boiling — the reference points were chosen by him, not by nature.
Why Pilots Care
Carburetor icing risk exists in specific Fahrenheit ranges, typically 20°F to 70°F when visible moisture is present.
Intuition Check
°F is not a special aviation temperature system. It is the ordinary Fahrenheit temperature scale used in many U.S. aviation publications.
Example Sentence 1
The outside air temperature gauge read 45 °F, well within the range where carburetor icing is possible.
Example Sentence 2
Fuel temperature remained above 32°F throughout the flight, reducing the chance of ice forming in the lines.