How long is a TEMPO valid for in a TAF?

In a Terminal Aerodrome Forecast (TAF), a TEMPO is a specific forecast for temporary fluctuations in weather conditions that are expected to occur within the overall forecast period. The validity of a TEMPO is set at 4 hours, which is why this option is the correct answer.

This duration is designed to account for short-term variations that are expected to be significant but brief and typically indicate changes in conditions such as visibility, precipitation, or wind, which can impact aviation operations. Understanding the validity of a TEMPO is crucial for flight dispatchers and pilots who need to assess weather risks and make informed decisions regarding flight safety and scheduling.

The other durations listed do not align with the official meteorological standards for TAFs, making them incorrect in this context.