Fine droplets of water or ice crystal suspended in the atmosphere; the World Meteorological Organization classifies them according to 10 types.
Gray sheet that can completely cover the sky but allows the Sun to be seen without a halo phenomenon; it can trigger heavy precipitation.
Cloud in the form of a dark layer sufficiently thick to block out the Sun; it triggers continuous precipitation.
Cloud composed of large white or gray flecks that sometimes form parallel layers; it foreshadows the arrival of a depression.
Cloud formed of white or gray flecks or strips, often arranged in rows.
Whitish layer that can completely cover the sky and that creates a halo around the Sun.
Cloud in the form of wisps or separate strips; it usually appears in advance of a depression.
Gray cloud forming a continuous veil that is similar to fog, though it never touches the ground; it can trigger light precipitation.
Very imposing cloud that can reach a thickness of 6 mi and whose base is very dark; it can trigger violent precipitation.
Fair-weather cloud with very clear contours; it has a gray, flat base and a white top with rounded protuberances.
Gray and white cloud arranged in more or less continuous rolled layers; it does not usually trigger precipitation.