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Cloud Classifications

There are four basic cloud classifications: cumulus, stratus, cirrus, and nimbus. Clouds are generally grouped according to height, as follows:

Name Symbol Description Name Symbol Description Name Symbol Description
Low Clouds Middle Clouds High Clouds
Cumulus Cumulus Little vertical development; flattened Altostratus Altostratus Thin, semi-transparent Cirrus Cirrus Filaments ("mares tails")
Cumulus Cumulus Considerable development; towering Altostratus Altostratus Thick; may hide sun or moon Cirrus Cirrus Dense, patchy
Cumulonimbus Cumulonimbus Tops lacking clear-cut outlines Altocumulus Altocumulus Thin, semi-transparent Cirrus Cirrus Dense, anvil-shaped
Stratocumulus Stratocumulus Spreading from cumulus Altocumulus Altocumulus Thin, patchy Cirrus Cirrus Hook-shaped; thickening
Stratocumulus Stratocumulus Not spreading from cumulus Altocumulus Altocumulus Bands; thickening Cirrus and cirrostratus Cirrus/cirrostratus Not reaching 45 altitude
Stratus and/or
fractostratus
Stratus and/or fractostratus Not bad weather Altocumulus Altocumulus Spreading from cumulus Cirrus and cirrostratus Cirrus/cirrostratus Exceeding 45 altitude
Fractostratus/
fractocumulus
Fractostratus/fractocumulus Bad weather (scud) Altocumulus Altocumulus Double layered Cirrostratus Cirrostratus Veil covering sky
Cumulus and
stratocumulus
Cumulus/stratocumulus Not spreading from cumulus Altocumulus Altocumulus Tufts or turrets Cirrostratus Cirrostratus Not increasing; not covering entire sky
Cumulonimbus Cumulonimbus Clear top; often anvil-shaped Altocumulus Altocumulus Chaotic sky Cirrocumulus Cirrocumulus Main cirriform cloud