What does cirrostratus mean?
Cirrostratus is a type of high-altitude cloud that forms a thin, smooth, whitish sheet across the sky at heights above roughly 20,000 feet. Made entirely of tiny ice crystals, it is thin enough for the sun or moon to be seen clearly through it, yet dense enough to refract their light into a distinctive ring-shaped halo — one of its most recognisable signatures. Because cirrostratus frequently precedes a warm front, its appearance has traditionally been read as a sign that wet or stormy weather may arrive within a day or so, a piece of folklore with genuine scientific grounding. The word derives from Latin roots: cirrus, meaning a curl or fringe, and stratus, meaning spread or layered, reflecting the cloud's combination of wispy high-altitude character and sheet-like form. It belongs to the formal vocabulary of meteorology, aviation, and nature writing, where it is used neutrally to classify and describe cloud cover rather than evoke emotion.
nounA thin, whitish layer of high cloud composed of ice crystals, typically covering the entire sky and often producing a halo effect around the sun or moon.
- A genus of high-altitude cloud (above about 20,000 ft) forming a thin, translucent, whitish sheet of ice crystals, often causing solar or lunar halos and traditionally regarded as a sign of approaching frontal weather.
"A milky veil of cirrostratus spread across the evening sky, ringed the moon with a faint halo, and hinted at rain within a day."
"By dawn a thin sheet of cirrostratus had veiled the entire sky, turning the sunrise into a pale wash of light."
"Sailors have long watched for cirrostratus halos as an early warning that a warm front — and rough weather — is approaching."
The plural follows the Latin-style pattern used for other cloud genera (e.g. cumuli), though it is rarely encountered outside technical meteorological writing; 'cirrostratus clouds' is the usual way to express multiplicity.
"Several distinct sheets of cirrostrati drifted across the upper atmosphere that afternoon."
Spot a ring around the sun or moon? You're almost certainly looking through cirrostratus — and folk meteorology says rain is on its way within a day.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cirrostratus
The term cirrostratus was coined in the early nineteenth century from two Latin elements: cirrus, meaning 'a curl or lock of hair,' applied by Luke Howard to wispy high clouds, and stratus, meaning 'spread out' or 'layered,' his name for low sheet-like cloud. The compound names a cloud that combines high, icy cirriform character with an extended stratiform sheet. It shares these roots with sibling terms such as cirrus, stratus, and cirrocumulus.
How cirrostratus is actually used
Cirrostratus is primarily a technical meteorological term but appears regularly in weather reporting, aviation contexts, and nature writing. It is always used in a neutral, descriptive register; there is no figurative or informal usage of note. The plural is rarely needed in ordinary prose.
Easily confused with cirrostratus
Cirrus refers to thin, wispy, individual streaks of high cloud, whereas cirrostratus forms a continuous, uniform sheet that can cover the whole sky.
Altostratus is a mid-level grey or blue-grey cloud layer thick enough to blur the sun, while cirrostratus is a higher, thinner, more transparent sheet that clearly shows the sun's outline and often produces halos.