What happens to the altimeter when flying into colder air?

When an aircraft ascends into colder air, the altimeter, which is designed to measure altitude based on air pressure, will indicate a higher altitude than the aircraft's actual position. This occurs because colder air is denser than warmer air, leading to higher pressure at a given altitude than would be found in warmer air. If the altimeter settings are not adjusted for the decreased temperature, it cannot accurately reflect the true altitude, resulting in a reading that is misleadingly high.

Thus, pilots must consider temperature variations when determining their altitude to ensure they are flying safely and within the correct airspace. Maintaining proper altimeter settings that account for temperature and pressure changes is crucial for accurate altitude readings, and understanding the effects of temperature on air density helps improve situational awareness and flight safety.