GlossaryStratus
Genus · Low · St
Stratus
Stratus
Definition
A genus of low cloud forming a generally grey, uniform layer with a fairly even base, not showing any distinct elements. It may produce drizzle or small snow grains, and it can reach the ground, at which point it is fog.
Field note
The distinguishing feature of stratus among cloud genera is that its base can be at the ground. When visibility falls below 1000 m the observation is recorded as fog rather than stratus.
- Added
- 8 July 2026
- By
- Class
- Genus
- Band
- Low
Read the full field note
Stratus: the cloud you are standing inside
Stratus is not really something you look at — it is something you are inside. It is a low, uniform grey layer with no visible elements, and its defining feature is that its base can be at the ground, at which point it is called fog. Nothing else in the sky has that property, and it changes how you observe it entirely.