This document provides information about common cloud types including their Latin names, typical altitudes and compositions. It classifies clouds into three levels - low, middle and high - based on their altitude in feet. Some key cloud types summarized are: Cumulus clouds form at low levels from 2,000-3,000 feet due to thermal convection. Cirrocumulus and cirrus clouds consist of ice crystals and form the highest at 16,500-45,000 feet. Nimbostratus clouds cause steady rain or snow and form thick gray blankets between 2,000-18,000 feet.

1. Common Cloud Names, Shapes, and Altitudes:

2. Genus Species (can be only one) Varieties (can be more than one) Cloud
humilis
Cumulus
mediocris
radiatus
Classification:
congestus
Low Clouds
fractus
Cumulonimbus calvus
(none)
Clouds are classified using a
(extend through all 3 levels) capillatus Latin “Linnean” system based
Stratus
nebulosus
opacus, translucidus, undulatus
on genera and species,
fractus originally developed by Luke
stratiformis translucidus, perlucidus, opacus, Howard, an amateur
Stratocumulus lenticularis duplicatus, undulatus, radiatus, meteorologist and Quaker in
castellanus lacunosus
1802.
Middle Clouds
stratiformus
lenticularis translucidus, perlucidus, opacus,
Altocumulus duplicatus, undulatus, radiatus, The modern classification
castellanus lacunosus
floccus
scheme is based on Howard’s
system and is detailed in The
translucidus, perlucidus, opacus,
Altostratus (none)
duplicatus, undulatus, radiatus
International Cloud Atlas,
published by the World
Nimbostratus
(extend through 1+ levels)
(none) (none) Meteorological Organization
fibratus
since 1896.
uncinus
intortus, radiatus, vertebratus, In addition to standardizing
Cirrus spissatus
High Clouds
duplicatus
castellanus the genus-species system, the
floccus WMO also classified clouds by
stratiformis altitude and divided the
lenticularis troposphere into 3 levels:
Cirrocumulus undulatus, lacunosus
castellanus
floccus Low-level Clouds: < 6,500 ft.
fibratus Mid-level Clouds: 6,500 to 23,000 ft.
Cirrostratus duplicatus, undulatus High-level Clouds: 16,500 to 45,000 ft.
nebulosus

3. Cumulus Clouds Fast Facts:
(“The cloud of choice for 6-yr.-olds”) Typical Altitude: 2,000-3,000 ft.
Location: Worldwide (except in
Antartica, where it’s too
cold)
Precipitation: Generally none, except for
brief showers from
There are three species of cumulus clouds: congestus
• humilis are wider than they are tall Composition: Liquid water
• mediocris are as wide as they are tall
Formation: Thermal convection currents
• congestus are taller than they are wide
Often called “fair-weather” clouds, cumulus clouds
are common over land on sunny days, when the sun
heats the land creating thermal convection currents
Each thermal is distinct, and, consequently, each
cumulus cloud is a distinct puff

4. Cumulonimbus Clouds Fast Facts:
(“The towering thunderclouds that scare us senseless”) Typical Altitude: 2,000-45,000 ft.
Location: Common in tropics and
temperate regions, rare at
Three critical conditions for cumulonimbus poles
formation: Precipitation: Heavy downpours, hail
Composition: Liquid water throughout,
• Ready supply of warm, moist air, which ice crystals at the top
rises at speeds of up to 25-70 mph
Formation: Upwardly mobile cumulus
congestus clouds (thermals)
• Tropospheric winds need to increase
considerably with height to encourage it to
slant forward
• The atmosphere around the cloud needs to
be “unstable” – no temp. inversions here

5. Stratus Clouds Fast Facts:
(“The clouds that weigh heavily on your mood”) Typical Altitude: 0-6,500 ft.
Location: Worldwide, but especially
Stratus clouds are the lowest forming and are often common around coasts and
called fog or mists when they are earth-bound mountains
Precipitation: No more than light drizzle
Stratus clouds are formed when
Composition: Liquid water
a large air mass cools at the
same time (e.g. – a warm air Formation: Advective or radiative
cooling
parcel drifts into or above a
cooler region)

6. Stratocumulus Clouds Fast Facts:
(“The low, puffy layers”) Typical Altitude: 2,000-6,500 ft.
Location: Worldwide – very common
Similar to cumulus clouds in form and composition, Precipitation: Occasional light rain, snow
stratocumulus clouds are textured and puffy, but also Composition: Liquid water
joined into a semi-continuous layer
Formation: Spreading and joining of
cumulus clouds below a
Stratocumulus clouds usually form from cumulus or temperature inversion, wind
turbulence in a stratus layer
stratus clouds

7. Altocumulus Clouds Fast Facts:
(“Layers of bread rolls”) Typical Altitude: 6,500-18,000 ft.
Location: Worldwide
Since altocumulus clouds are high in the sky, they are Precipitation: Very occasional light rain
generally above the influence of thermals, and form Composition: Mostly liquid water, may
very differently from cumulus and stratocumulus clouds, also contain ice crystals
who share similar names. Formation: Mid-level atmospheric
disturbances and wave
propagation (from e.g. –
mountatins)

8. Altostratus Clouds Fast Facts:
(“The boring clouds”) Typical Altitude: 6,500-16,500 ft.
Location: Worldwide, common in middle
latitudes
Below 6,500 ft. it’s stratus
Precipitation: Occasional light rain, snow
Between 6,500 and 23,000 ft. it’s altostratus Composition: Both liquid water, and ice
crystals
Boring! – but being so high up, they do make for nice Formation: Usually formed from the
thickening and lowering of a
sunsets. cirrostratus cloud on its way
to becoming a nimbostratus
cloud
Altostratus Altocumulus
Altostratus are potentially dangerous
to aircraft because they can cause ice
accumulation on the wings.

9. Nimbostratus Clouds Fast Facts:
(“Rainy day clouds”) Typical Altitude: 2,000-18,000 ft.
Location: Worldwide, common in middle
latitudes
The nimbostratus cloud has no species or varieties.
Precipitation: Moderate to heavy rain or
It is a thick, wet blanket with a ragged base caused by snow, which is generally
the continual precipitation steady and prolonged
Composition: Liquid water, raindrops
snowflakes and ice
crystals
Formation: Usually formed from the
thickening and lowering of a
altostratus cloud

10. Cirrus Clouds Fast Facts:
(“Delicate cloud streaks”) Typical Altitude: 16,500-45,000 ft.
Cirrus clouds are the highest of all clouds and are Location: Worldwide
composed entirely of ice crystals. Precipitation: None that reaches ground
Composition: Ice crystals
Cirrus clouds are precipitating clouds, although the
ice crystals evaporate high above the earth’s surface. Formation: Fall streaks of ice crystals in
upper troposphere winds
The crystals, caught in 100-150 mph winds create
wisps of cloud.

11. Cirrocumulus Clouds Fast Facts:
(“Regularly spaced cloudlets, often rippled”) Typical Altitude: 16,500-45,000 ft.
Location: Worldwide
Cirrocumulus clouds are usually a transitional phase
Precipitation: None that reaches ground
between cirrus and cirrostratus clouds.
Composition: Ice crystals
Large numbers of cirrocumulus clouds may indicate Formation: Cloudlets formed by choppy
poor weather is approaching. winds and high moisture
levels in upper troposphere

12. Cirrostratus Clouds Fast Facts:
(“Delicate cloud streaks”) Typical Altitude: 20,000-42,000 ft.
Location: Worldwide
Cirrostratus clouds are difficult to spot and appear as
Precipitation: None
a pale, milky lightening of the sky.
Composition: Ice crystals
Cirrostratus clouds never block out the sun Formation: Spreading and joining of
completely, but rather produce a variety of optical cirrus clouds
effects.

13. Contrails and Others
cirrus
cirrostratus
cirrus
contrails Kelvin-Helmholtz Wave Clouds
Cumulus