Definition
The actual outside air temperature existing at a given location and time, as opposed to the temperature defined by a standard atmospheric model.
Plain English
The real temperature of the air around you right now, not a textbook number.
Context Anchor
Seen in maintenance instructions, weather discussions, and performance references when the temperature must match the real conditions at the aircraft or airport.
Derivation
From Latin praevalere, meaning 'to be stronger' or 'to predominate.' Here it carries the sense of 'currently in effect' — the temperature that is actually present at the time, not a predicted or theoretical value.
Why Pilots Care
Aircraft and engine performance are published against standard temperatures. Knowing the prevailing temperature lets a pilot or technician judge how performance, density altitude, and engine behavior will differ from the book values.
Intuition Check
Do not read “prevailing” as “usual” or “average.” Here it means the temperature actually present at that location and moment.
Example Sentence 1
With a prevailing temperature well above standard, the technician expected a noticeable drop in takeoff performance.
Example Sentence 2
Performance tables require the prevailing temperature to be entered before calculating takeoff distance on a hot day.