Altostratus Clouds: Mid-altitude Gray Layer

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Definition: Sheet of featureless, gray clouds in the middle cloud level capable of masking the sun

Description & Characteristics. Altostratus clouds are found in the middle cloud level. And unlike their altocumulus counterpart, they’re often boring to look at. Along with nimbostratus clouds, these clouds don’t have any species associated with them.

But they do come with a handful of cloud varieties, which can help you make the determination if you’re looking at an altostratus cloud or not. If you see a cloud covering the sky’s entirety that’s not very close to the ground, and it’s positioned such that it’s visible through the clouds but giving off a ‘frosted glass’ appearance, chances are good that you’re observing an altostratus translucidus cloud. On the flip side, if the cloud is opaque and you can’t see the sun’s position, then consider it an altostratus opacus.

These clouds can also be responsible for precipitation, though it’s short-lived and not very common. You might also find scud clouds (pannus cloud accessory) underneath the main cloud layer, which can be one more indication that you’re looking at an altostratus cloud.

Altostratus opacus (As op)
Altostratus translucidus (As tr)
Altostratus undulatus (As un)
Altostratus translucidus (As tr)
Altostratus translucidus (As tr)
Altostratus (As)
Altostratus opacus (As op)
A photograph of altostratus opacus clouds (As op) over a field

Altostratus Cloud Facts

  • Cloud Level (Étage): ….. Middle
  • Altitude/Height: ……… 2-7km (7,000-23,000 ft)
  • Latin Term: …………… Derives from alto-, meaning high, and strato- meaning layer
  • Abbreviation: ………… Altostratus can be abbreviated as As
A bar graph showing the visual color of an altostratus cloud

Cloud Color

Gray to dark gray

A bar graph showing the precipitation potential of an altostratus cloud

Precipitation Potential


A bar graph showing the amount of sky cover from an altostratus cloud

Sky Cover

Cloudy to mostly cloudy

A bar graph showing how common observing a cirrostratus cloud might be

Cloud Frequency


Altostratus Cloud Species

Roses are red, and everyone likes freebies, but altostratus clouds have no associated cloud species. ⛅

Altostratus Cloud Varieties

Altocumulus clouds have five associated cloud varieties: duplicatus, opacus, radiatus, translucidus, and undulatus.

A graphical illustration of an altostratus opacus cloud

Altostratus opacus

Opaque, masks the sun

A graphical illustration of an altostratus radiatus cloud

Altostratus radiatus

Parallel bands and strips

A graphical illustration of an altostratus translucidus cloud

Altostratus translucidus

See-through, sun’s position visible

A graphical illustration of an altostratus undulatus cloud

Altostratus undulatus

Wavelike, undulating

Altostratus Cloud Supplementary Features

Altostratus clouds have three supplementary features: mamma, praecipitatio, and virga.

A graphical illustration of an altostratus mamma cloud

Altostratus mamma

Sac-like, resembling cow udders

A graphical illustration of an altostratus praecipitatio cloud

Altostratus praecipitatio

Precipitation reaching the surface

Altostratus virga

Evaporating rain strips

Altostratus Cloud Accessories & Other Clouds

Altostratus clouds have only one associated accessory cloud: pannus.

A graphical illustration of an altostratus pannus cloud

Altostratus pannus

Ragged frazzles, scud

Similar Cloud Types

Altostratus vs. Altocumulus

While altostratus and altocumulus clouds are found at the same altitude, altostratus clouds are generally a featureless layer, where altocumulus clouds typically have plenty of features. Altostratus clouds don’t have any cloud species associated with them, so if you’re deciding between an altostratus and altocumulus cloud and the cloud you’re observing looks to have an associated cloud species, you should learn towards an altocumulus cloud.

Altostratus vs. Cirrostratus

Altostratus and cirrostratus clouds are both layer clouds. A key difference is that if you see an optical phenomena in a cloud and are trying to decide between the two, you’re probably looking at a cirrostratus cloud. Cirrostratus clouds are lighter in color, you can always see the sun’s position through a cirrostratus cloud, which is not always the case with altostratus clouds, which are darker and lower to the ground than cirrostratus clouds.

Altostratus vs. Stratocumulus

Altostratus clouds are generally a featureless layer cloud, whereas stratocumulus clouds have more detail. Remember, if you’re trying to decide between an altostratus and stratocumulus cloud, and the cloud being observed has been determined to have an associated cloud species, it’s not an altostratus cloud.

Altostratus vs. Stratus

Both altostratus clouds and stratus clouds are both layer clouds, so they can certainly look the same. Altostratus clouds are higher in altitude though, which means they won’t touch the ground or mask the tops of tall buildings like a stratus cloud would. When deciding between these clouds, if you’re able to see further off in the distance, chances are likely that you’re looking at an altostratus cloud.