Cloud Types: The Ten Cloud Forms

Every cloud has a name, and the name tells you something.

Meteorologists sort clouds into ten main forms by their shape and height. Learn a few Latin words and a handful of clues, and the sky starts to read like a forecast.

Updated 15 October 2026 · 6 sources

Look at the shape
Judge the height
Watch how it changes
Three clues, ten cloud forms

Name a cloud

THE SHORT ANSWER

Ten forms,
three heights.

The World Meteorological Organization lists ten main cloud groups.
Each cloud belongs to one, and only one.

LOW

Heaps and blankets

Cumulus are the puffy, cauliflower-shaped clouds of fair days. Stratus is the flat grey blanket, sometimes low enough to be mist or fog.

Name a cloud

STORM

The king of clouds

Cumulonimbus can tower through the whole lower atmosphere. The Met Office says it is the only cloud that can produce hail, thunder and lightning.

See the numbers

HIGH

Wisps of ice

Cirrus floats at 20,000 to 40,000 ft and is made entirely of ice crystals. It often forms ahead of a warm front, a sign the weather may change.

How to spot them

High wispy cirrus clouds streaked across a deep blue sky, with fine hooked tails like strands of hair — AI-generated image, not a photograph of a real person or place.

HOW TO SPOT THEM

Look up,
then look again.

You do not need any equipment. Weather observers do the same three things: judge the height, read the shape and watch how the sky changes.

Judge the height
Over the British Isles, low cloud bases sit below 6,500 ft, mid-level ones between 6,500 and 20,000 ft and high ones above 20,000 ft.
Read the shape
Heaped and puffy is cumulus, flat and layered is stratus, and high and wispy is cirrus. Most names combine these.
Check for shadows
The Sun still casts shadows through thin cirrostratus but often cannot through altostratus, which helps tell the two apart.
Watch it change
Cumulus can grow into cumulonimbus during a day, and altostratus can thicken into rain-bearing nimbostratus as a front arrives.

TWO NUMBERS WORTH KNOWING

A cloudy planet,
and its commonest cloud.

One figure for how much of Earth is under cloud,
one for the cloud that covers the most of it.

≈ 67%

Share of Earth's surface typically under cloud

NASA's Earth Observatory says one study, based on nearly a decade of satellite data, estimated that about 67 percent of Earth's surface is typically covered by clouds.

CLOUD COVER · NASA

≈ 1/5

Earth's surface covered by stratocumulus

Marine stratocumulus is the most common cloud type in the world by area. NASA says stratocumulus typically covers about one fifth of Earth's surface.

STRATOCUMULUS · NASA

NASA also notes that over the oceans less than 10 percent of the sky is completely clear at any one time, while over land about 30 percent of skies are cloud free.

WHAT CLOUD IS THAT?

What can you see
overhead?

Pick the cloud that best matches your sky to see what the Met Office says it usually brings. The bar shows how likely that cloud is to mean wet or changing weather.

Based on the Met Office's guides to low, mid-level and high clouds. Clouds are clues, not a forecast: check an official forecast before heading out.

Sky check

Choose a cloudSmall white puffs, flat basesLow, flat grey blanketHigh, thin wisps or a halo round the SunThick, dark grey sheet hiding the SunHuge tower with an anvil top

Small white puffs, flat basesFair weather

Probably cumulus. The Met Office says it mostly indicates fair weather, though on warm days it can grow taller and bring showers.

Low, flat grey blanketDrizzle at most

Probably stratus. It usually brings little or no rain, but a thick layer can produce light drizzle, or light snow if it is cold enough.

High, thin wisps or a halo round the SunChange coming

Cirrus or cirrostratus. Both often form ahead of a warm front. A veil-like cirrostratus layer can mean persistent rain within a day.

Thick, dark grey sheet hiding the SunSteady rain

Probably nimbostratus. It brings continuous moderate rain or snow that may last several hours until the front passes.

Huge tower with an anvil topStorms likely

Cumulonimbus. It can bring torrential downpours, hail and lightning. A single cell usually dies out within an hour once the showers start.

Source: Met Office, Low level clouds, Mid-level clouds and High clouds.

A towering cumulonimbus storm cloud with a spreading anvil top rising above dark rain-filled lower cloud — AI-generated image, not a photograph of a real person or place.

WHERE THE NAMES CAME FROM

A pharmacist
named the sky.

The Met Office says cloud classification was first proposed in 1802 by Luke Howard, a London pharmacist and amateur meteorologist. His three main types, stratus, cumulus and cirrus, are still the basis of the system we use today.

The World Meteorological Organization later extended Howard's scheme into ten main groups called genera. Its International Cloud Atlas gives observers around the world a common language, so a cumulus reported in Britain means the same as one reported anywhere else.

In conversation

Questions people ask

How many types of cloud are there?

The World Meteorological Organization's International Cloud Atlas lists ten main groups, called genera. Each observed cloud belongs to one, and only one, genus. Most genera are then divided into species and varieties.

What do the Latin cloud names mean?

Stratus means flat or layered, cumulus means heaped up, cirrus means high and wispy, alto means medium level and nimbus means rain-bearing. Nimbostratus, for example, is a flat, layered cloud that can bring rain.

What is a cloud made of?

Tiny water droplets, about a hundredth of a millimetre across, or ice crystals if the cloud is high and cold enough. The Met Office explains that water vapour itself is invisible; it is the condensed droplets that make a cloud visible.

Which cloud brings thunderstorms?

Cumulonimbus. The Met Office says it is the only cloud type that can produce hail, thunder and lightning. If there is thunder, lightning or hail, the cloud is a cumulonimbus rather than a nimbostratus.

What is a mackerel sky?

Cirrocumulus can look like the scaly skin of a fish and is then called a mackerel sky. The Met Office says it is usually linked with fair weather, but its appearance can come before stormier weather.

Sources

Each figure on this page comes from the sources below.

Read the sky,
one cloud at a time.