Definition
A unit of temperature measurement on the Celsius scale, where water freezes at 0°C and boils at 100°C at standard sea-level pressure. It is the standard temperature unit used in aviation weather reports, performance charts, and most international pilot operations.
Plain English
A way of measuring how hot or cold something is. Zero is freezing water, one hundred is boiling water, and most aviation temperature numbers you'll see use this scale.
Context Anchor
Seen in weather reports, aircraft temperature readings, and carburetor icing charts in FAA training material.
Derivation
Named after Anders Celsius, the Swedish astronomer who proposed the scale in 1742. The small circle (°) is the degree symbol, used for temperatures and angles alike.
Why Pilots Care
Temperature readings in Celsius directly affect decisions about carburetor heat, density altitude, and engine performance.
Intuition Check
Do not read the degree symbol here as an angle. In °C, it means degrees of temperature on the Celsius scale.
Example Sentence 1
The METAR reported the outside air temperature as 15°C, well within the range where carburetor icing can occur in humid conditions.
Example Sentence 2
Converting the outside air temperature to Celsius allowed accurate calculation of density altitude.