What temperature is considered a "standard day"?

A "standard day" is defined by specific atmospheric conditions that are used as a baseline for various calculations in aviation, including performance metrics and density altitude. The standard temperature at sea level is established as 15 degrees Celsius or 59 degrees Fahrenheit. This standardization helps pilots and meteorologists communicate and understand the effects of temperature on aircraft performance consistently.

In aviation, temperatures other than the standard can affect the aircraft's lift, engine performance, and overall behavior in the air, so understanding this benchmark is essential. The other temperature options provided exceed the standard temperature for a "standard day," making them unsuitable as a reference for typical performance calculations in aviation settings.