SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/ifr-cold-weather-altimeter

On a very cold day with the correct altimeter setting, how does your true altitude compare with indicated?

True altitude is lower than indicated in colder than ISA air.

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  1. Lower, so obstacle clearance shrinks ✔
  2. Higher, so you have extra clearance
  3. Identical, since the setting corrects temperature

Why: Altimeters are calibrated to standard atmosphere temperatures. In air colder than ISA, true altitude is lower than indicated altitude, which can reduce obstacle clearance.

Huh, didn't know that: For cold temperature corrections, coordinate planned intermediate or missed approach holding corrections with ATC; final segment corrections do not need to be reported.

The dad joke
Cold air told the altimeter to lower its expectations.
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References

Answer: Lower, so obstacle clearance shrinks. Altimeters are calibrated to standard atmosphere temperatures. In air colder than ISA, true altitude is lower than indicated altitude, which can reduce obstacle clearance.

  1. FAA Instrument Flying Handbook (FAA-H-8083-15B) www.faa.gov/sites/faa.gov/files/pilots/FAA-H-8083-15B.pdf
    true altitude being lower than indicated altitude whenever the temperature is colder than ISA
    Checked 2026-10-11.
  2. AIM 5-5 Pilot/Controller Roles and Responsibilities www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_5.html
    Pilots do not have to advise ATC of a correction in the final segment.
    Checked 2026-10-11.

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