Definition
Weather conditions in which cloud bases, visibility, or both are near the minimum values that allow flight under Instrument Meteorological Conditions (IMC) — typically low ceilings, reduced visibility, and limited room for error during instrument approaches and departures.
Plain English
Bad weather where the clouds are very low and you can't see far, so a pilot must rely almost entirely on instruments to fly safely.
Context Anchor
Seen in instrument training when discussing actual weather conditions used to teach instrument flying, especially departures and approaches in clouds or poor visibility.
Derivation
‘Low’ refers to low ceilings (the height of the cloud base above the ground) and low visibility. ‘IMC’ stands for Instrument Meteorological Conditions — weather below the minimums required to fly visually. Together, ‘low IMC’ describes the more challenging end of instrument weather.
Why Pilots Care
Low IMC is where instrument flying skills are tested most. There is little visual reference, less margin for mistakes on approaches, and a higher workload. Pilots train specifically so they can handle these conditions safely rather than avoid them by accident.
Grounding Statement
Picture climbing after takeoff and entering cloud a few hundred feet above the runway; that is the kind of situation pilots mean by low IMC.
Intuition Check
Low does not mean the airplane is flying low by itself. Here, low mainly refers to the cloud base or visibility being close to the ground.
Example Sentence 1
The instructor planned the lesson for a day of low IMC so the student could practice an approach down to near-minimum visibility.
Example Sentence 2
During the flight the student maintained altitude precisely while operating in low IMC.