Definition
A weather category indicating ceilings between 1,000 and 3,000 feet above ground level and/or visibility between 3 and 5 statute miles inclusive. Conditions are still legal for VFR flight in most airspace, but the margin between visual conditions and instrument conditions is reduced.
Plain English
Weather that is technically clear enough to fly by looking outside, but only just. The clouds are lower and the visibility is shorter than ideal, so a pilot has less room for error.
Context Anchor
Seen in aviation weather reports, forecasts, flight planning tools, and weather briefings, often abbreviated as MVFR.
Derivation
Marginal comes from the Latin margo, meaning edge or border. MVFR weather sits at the edge of what counts as visual flying conditions — better than instrument weather, worse than clear VFR.
Why Pilots Care
These conditions require pilots to decide whether to continue under VFR, switch to IFR, or delay the flight for safety and legal compliance.
Grounding Statement
Picture flying under a low cloud layer on a hazy day: you can still see outside, but the sky and horizon do not give you much extra space or comfort.
Intuition Check
Marginal does not automatically mean illegal or unsafe. It means the visual weather is near the lower limit, so the pilot must be careful about the exact conditions and the rules that apply to the flight.
Example Sentence 1
The morning briefing showed MVFR conditions along the route, with ceilings around 2,000 feet and visibility near 4 miles.
Example Sentence 2
Even in marginal visual flight rules the student pilot maintained visual contact with the ground while heading back to the airport.