When flying into extremely cold conditions, how does the aircraft's altitude relate to the altimeter indication?

In extremely cold conditions, the aircraft's altitude indication can be affected due to the fact that altimeters rely on the properties of the atmosphere to measure altitude based on air pressure. When temperatures are significantly colder than standard atmosphere conditions, the air density alters, and consequently, the altimeter may read higher than the true altitude.

In these conditions, the altimeter assumes a standard temperature lapse rate and may not compensate adequately for the colder temperatures present. As a result, the aircraft is actually lower than what the altimeter indicates, leading to potentially hazardous situations if not accounted for. Pilots need to adjust their altitude calculations to account for this discrepancy, ensuring safe operation in challenging weather conditions.