Definition
A change indicator used in a Terminal Aerodrome Forecast (TAF) to show that the forecast conditions following it are expected to occur for periods of less than one hour at a time, and in total are not expected to cover more than half of the time period that follows the indicator. The TEMPO group is followed by a beginning and ending time, and the conditions inside the group are temporary fluctuations within that window — not the prevailing weather.
Plain English
TEMPO marks a short-lived change in the weather forecast. The conditions listed after it are expected to come and go briefly during the stated time window, not to last the whole period.
Context Anchor
Seen in airport weather forecasts when conditions such as visibility, ceiling, wind, or precipitation may change for short periods.
Derivation
TEMPO is shortened from temporary, from the Latin tempus meaning time. The aviation use keeps that root meaning — something tied to a limited stretch of time rather than the steady, prevailing condition.
Why Pilots Care
Pilots use the distinction to decide whether a forecast hazard will affect their flight or can be waited out.
Intuition Check
Do not read TEMPO as meaning the weather will stay that way for the whole forecast period. It means the listed conditions may happen briefly within the stated time window.
Example Sentence 1
The TAF showed visibility of six miles, with TEMPO 1820/1823 3SM -SHRA, so the pilot planned for the chance of brief rain showers and reduced visibility on arrival.