How high up are clouds?

It depends on the type. Low clouds like stratus sit close to the ground, sometimes only a few hundred metres up. High clouds like cirrus can be 6 kilometres or more above us, where the air is freezing cold.

Why are clouds white but storm clouds look grey or black?

Thin clouds let lots of sunlight through and scatter it, so they look bright white. Thick storm clouds are so full of water that light cannot pass through, so they look dark grey or black from below.

Why do clouds float instead of falling?

The water droplets in a cloud are incredibly tiny and light, and rising warm air keeps pushing them up. They only fall as rain once they join together and grow heavy enough.

Types of Clouds | Nature

What is a cloud, really?

Look up on almost any day and you will see clouds. They might be puffy and white, thin and feathery, or a flat grey sheet that hides the Sun. A cloud is not solid like cotton wool — it is made of millions of tiny water droplets and ice crystals floating in the air.

So where do these droplets come from? The air around us always holds some water that we cannot see, called water vapour. When warm air near the ground rises, it cools down as it climbs higher. Cool air cannot hold as much water vapour, so the vapour turns back into tiny liquid droplets. This change is called condensation, and it is exactly how a cloud is born. The same thing happens in miniature when you breathe out on a cold day and see a little "cloud" of mist.

Clouds are a key part of the journey water takes around our planet. If you want to see how it all connects, read about the water cycle.

Why scientists sort clouds

There are clouds of every size and shape, so scientists give them names. They sort clouds in two ways:

By their shape — is the cloud puffy and lumpy, or flat and spread out, or thin and wispy?
By their height — is it low near the ground, in the middle of the sky, or very high up?

The names use Latin words. Cirrus means "a curl of hair", cumulus means "a heap", stratus means "a layer", and nimbus means "rain". Scientists mix these words together to describe each cloud. Once you know the four main families below, you can name most of the clouds you see.

The four main types of cloud

Cirrus — high and wispy

Cirrus clouds live very high in the sky, often more than 6 kilometres up where the air is freezing. Because they are so high and cold, they are made of ice crystals, not water droplets. They look like thin white feathers, curls or streaks brushed across a blue sky. On their own, cirrus clouds usually mean fair weather, but if more and more of them appear, they can be an early sign that wet weather is on the way in a day or two.

Cumulus — puffy and white

Cumulus clouds are the puffy, cotton-wool clouds with flat bottoms and lumpy tops, a bit like a cauliflower. You see them most on warm, sunny days when the Sun heats the ground and bubbles of warm air rise. Small cumulus clouds with lots of blue sky around them mean fair weather. But if they keep growing taller and taller through the afternoon, they can build into storm clouds.

Stratus — flat grey sheets

Stratus clouds spread out as a low, flat, grey blanket that can cover the whole sky. On a stratus day the Sun is hidden and the light is dull. These clouds often bring drizzle or light, steady rain. When a stratus cloud touches the ground, we call it fog — so fog is really just a cloud you can walk through.

Cumulonimbus — towering storm clouds

Cumulonimbus is the giant of the cloud world. It starts like a cumulus cloud but grows enormously tall, sometimes reaching the very top of the part of the air where weather happens. The top often flattens out into an anvil shape, like a blacksmith's tool. These clouds bring heavy rain, thunder and lightning, strong winds and sometimes hail. If you see a dark, towering cloud with a flat anvil top, a storm is likely coming.

Reading the weather from clouds

People have watched clouds to guess the weather for thousands of years, long before there were weather apps. The clues are real:

Thin, high cirrus turning into a milky white sky → rain may arrive in a day or so.
Small, scattered puffy cumulus → a fine, settled day.
A low grey stratus sheet → dull and drizzly.
A dark, towering cumulonimbus → take shelter, a storm is near.

Clouds are part of the bigger pattern of weather over each part of the world. To explore how that works, see climate and weather.

Activity: become a cloud-watcher

Try this weather-watch activity for a week.

Each day at the same time, go outside and look up.
Decide which main type of cloud you can see: cirrus, cumulus, stratus or cumulonimbus. You might see more than one kind.
In a notebook, write the date, the cloud type, and a quick sketch. Note how much of the sky is covered — none, half, or all of it.
Also write down the weather that day: sunny, cloudy, rainy or windy.
After a week, look back. Did puffy cumulus go with sunny days? Did grey stratus go with rain? See if you can use the clouds to predict the next day's weather, then check if you were right.

The more you watch the sky, the better you will get at reading the clouds — just like real weather scientists do.

Types of Clouds

Key takeaways