Definition
Atmospheric conditions, other than clouds, that reduce visibility by hiding all or part of the sky and surrounding terrain from view. Common obscuring phenomena include fog, haze, smoke, dust, blowing snow, sand, and volcanic ash. When such phenomena hide the sky, the condition is reported as an obscuration; when they reduce horizontal visibility but do not hide the sky, the condition is reported as a partial obscuration.
Plain English
Things in the air -- other than clouds -- that make it hard to see, such as fog, smoke, haze, dust, or blowing snow. They can block your view of the sky, the ground, or both.
Context Anchor
Seen in aviation weather reports, forecasts, and flight-planning decisions when visibility or sky conditions may affect a flight.
Derivation
From the Latin obscurare, meaning 'to darken' or 'to hide.' The term literally describes anything in the atmosphere that hides what the pilot would otherwise be able to see.
Why Pilots Care
These conditions decide whether VFR flight is possible and directly affect safe navigation and landing.
Grounding Statement
Picture trying to see a runway through thick fog or blowing snow; the runway may still be there, but the air between you and it is blocking your view.
Intuition Check
Do not assume obscuring phenomena means clouds only. In aviation, it usually refers to things in the air near or around the pilot—like fog, smoke, dust, or snow—that block visibility.
Example Sentence 1
The METAR reported smoke as an obscuring phenomenon, dropping visibility to one mile despite a clear sky above.
Example Sentence 2
The pilot delayed departure until the obscuring phenomena cleared and the horizon became visible again.