Definition
A cloud type characterized by a uniform, layered, sheet-like structure with a flat or featureless base, typically forming at low altitudes. Stratus clouds form when a stable layer of moist air is cooled to its dew point, often producing overcast skies, mist, drizzle, or low ceilings and reduced visibility.
Plain English
A flat, gray sheet of cloud that sits in a low, even layer across the sky — the kind that makes a day look overcast and dull, often producing mist or drizzle.
Context Anchor
Seen in weather discussions about fog, low clouds, and conditions that may reduce visibility near the surface.
Derivation
From the Latin stratus, meaning 'spread out' or 'layered' (the past participle of sternere, 'to spread'). The name fits the cloud's appearance: a layer spread evenly across the sky, rather than piled up like a cumulus cloud.
Why Pilots Care
Stratus often creates low ceilings and reduced visibility that can force a shift to instrument flight or prevent departure under visual rules.
Analogy
Stratus is like a low blanket spread across the sky. Fog is like that same blanket lying on the ground around you.
Grounding Statement
Picture a low, gray, featureless ceiling stretched flat across the sky on a damp morning — that's stratus.
Intuition Check
Do not think of stratus as a tall, building storm cloud. Stratus is mainly a flat, layered cloud, and its main concern for pilots is how low it sits and how much it limits visibility.
Example Sentence 1
The morning briefing showed a stratus layer at 800 feet, so the pilot delayed departure until the ceiling lifted.
Example Sentence 2
We flew just below the stratus layer to maintain visual contact with the ground during the short cross-country.