Definition
A change indicator used in a Terminal Aerodrome Forecast (TAF) to show that the forecast conditions are expected to occur for periods of less than one hour at a time, and in total are expected to last less than half of the indicated time period. TEMPO is followed by a four-digit time group showing the beginning and ending hours during which the temporary conditions are expected.
Plain English
TEMPO marks weather that is expected to come and go briefly during a stated window, rather than settling in. Each occurrence lasts under an hour, and added together they cover less than half of the window.
Context Anchor
You will see TEMPO in airport weather forecasts, especially when checking expected visibility, clouds, wind, or weather before a departure or arrival.
Derivation
From the Latin tempus, meaning 'time.' The same root gives us 'temporary' and 'tempo' in music. In a TAF, it flags conditions that are short-lived rather than lasting.
Why Pilots Care
It helps pilots decide whether a brief period of marginal weather will affect their planned arrival or departure time.
Intuition Check
TEMPO does not mean the condition is unimportant or unlikely. It means the condition is expected to happen briefly or off and on during the stated time window.
Example Sentence 1
The TAF showed TEMPO 1822 3SM TSRA, so the pilot planned for possible thunderstorms with reduced visibility between 1800Z and 2200Z.
Example Sentence 2
Because the forecast showed TEMPO conditions for crosswinds, the pilot waited thirty minutes before attempting the approach.