In hot weather, how will an altimeter behave?

In hot weather, an altimeter will under-read the actual altitude. This behavior occurs because the altimeter is calibrated to standard atmospheric conditions, which include a specific temperature profile. Specifically, the altimeter relies on the concept that air density decreases with altitude and that temperature also plays a crucial role in this process.

When the temperature is higher than standard conditions, the density of the air is reduced. As a result, an aircraft flying at a certain altitude in warmer air will be at a higher physical elevation than indicated by the altimeter, which is based on lower density air assumptions. Therefore, the altimeter reading will be lower than the aircraft's true height above ground level, leading to the under-reading phenomenon.

Understanding this is vital for pilots, as they must be aware of how changes in temperature can affect altitude readings. In practice, this means that during hot weather, careful adjustments and considerations must be made when interpreting altimeter readings to ensure safe navigation and altitude awareness.