If an aircraft's altimeter is set to airport elevation at a high temperature, what will happen if the temperature drops significantly?

When an aircraft's altimeter is set to the airport elevation at a high temperature, it is calibrated based on the standard atmospheric conditions. As temperatures drop significantly, the density of the air changes, and this affects the altimeter reading. Altimeters are designed to measure the air pressure, which correlates with altitude. However, as the temperature decreases, the air becomes denser, which results in a pressure change.

When the aircraft is in colder air, the altimeter continues to read based on the previous setting made during warmer conditions. Consequently, it interprets the compressed air around it as being at a higher altitude than it actually is. Therefore, the altimeter will show a higher altitude than what the aircraft is truly at in colder conditions, making it essential for pilots to adjust their altimeter settings according to changes in temperature and pressure to ensure accurate altitude readings.