Cirrus clouds are the very high clouds that look like thin streaks or
curls. They are usually 6 kilometers (4 miles) or more above the earth
and are usually a sign of fair weather. In cold climates, however,
cirrus clouds that begin to multiply and are accompanied by increasing
winds blowing steadily from a northerly direction indicate an oncoming
Cumulus clouds are fluffy, white, heaped-up clouds. These clouds,
which are much lower than cirrus clouds, are often fair weather clouds.
They are apt to appear around midday on a sunny day, looking like large
cotton balls with flat bottoms. As the day advances, they may become
bigger and push higher into the atmosphere, piling up to appear like a
mountain of clouds. These can turn into storm clouds.
Stratus clouds are very low, gray clouds, often making an even gray
layer over the whole sky. These clouds generally mean rain.
Nimbus clouds are rain clouds of uniform grayness that extend over
the entire sky.
Cumulonimbus is the cloud formation resulting from a cumulus cloud
building up, extending to great heights, and forming in the shape of an
anvil. You can expect a thunderstorm if this cloud is moving in your
Cirrostratus is a fairly uniform layer of high stratus clouds that
are darker than cirrus clouds. Cirrostratus clouds indicate good
Cirrocumulus is a small, white, round cloud at a high altitude.
Cirrocumulus clouds indicate good weather.
A loose, vapory cloud (scud) driven before the wind is a sign of
continuing bad weather.