Definition
An additive altitude correction applied to indicated altitude to compensate for the fact that a pressure altimeter overreads (shows the aircraft higher than it actually is) when the air is colder than the standard atmosphere. The correction is required at designated cold temperature airports and on certain instrument procedure segments when the reported surface temperature is at or below a published threshold, and is calculated using a standard ICAO cold temperature correction table based on the height above the altimeter setting source.
Plain English
When the air is much colder than normal, your altimeter shows you higher than you really are. To stay safely above terrain and obstacles on an instrument approach, you add a published number of feet to your altitude so the aircraft is actually flying at the height the procedure intended.
Context Anchor
Seen during instrument approach planning, especially for airports and procedures identified as needing cold-weather altitude corrections.
Why Pilots Care
Failure to apply the correction can result in dangerously low actual altitudes during the approach, increasing the risk of controlled flight into terrain.
Grounding Statement
On a very cold approach, the number shown on the altimeter can look safe while the aircraft is actually closer to the ground than expected.
Intuition Check
Do not assume this means adjusting the altimeter setting or correcting the temperature itself. It means adding altitude to certain published altitudes because cold air can make indicated altitude misleading.
Example Sentence 1
Because the reported temperature was minus 25 Celsius, the crew applied a cold temperature correction to the final approach segment and advised ATC of the corrected altitude.
Example Sentence 2
During the approach briefing the crew reviewed the cold temperature correction table for the -15 °C surface temperature reported at the airport.