Definition
Low-level clouds that form in flat, uniform, horizontal layers or sheets, typically with a featureless gray appearance and little vertical development. They form when a stable layer of moist air is cooled to its dew point, often producing overcast skies, light drizzle, or reduced visibility, and are closely related to fog (which is essentially a stratus cloud at the surface).
Plain English
A flat, gray layer of cloud that spreads out like a sheet across the sky. It usually sits low, blocks the sun, and can bring drizzle or poor visibility.
Context Anchor
Seen in weather reports, preflight weather briefings, and fog discussions when low cloud layers may affect departure, approach, or visibility near the airport.
Derivation
From the Latin stratus, meaning 'spread out' or 'layered.' The name fits the cloud's appearance: a smooth, spread-out sheet rather than a piled-up heap.
Why Pilots Care
They signal stable air but often bring low ceilings and reduced visibility that can force IFR flight or prevent VFR departures.
Grounding Statement
Picture a flat gray ceiling stretched across the sky from horizon to horizon -- no shape, no texture, just a uniform layer of cloud sitting low overhead.
Intuition Check
Do not think of stratus clouds as tall, towering clouds. Stratus clouds are mainly a low, spread-out layer; if that layer reaches the ground, it is fog.
Example Sentence 1
The morning briefing showed stratus clouds at 800 feet across the entire region, so the pilot filed IFR instead of attempting the flight under VFR.
Example Sentence 2
With stratus clouds overhead, the approach was flown with reduced visibility but steady winds.