Meteorologists study the weather

Instruments on a weather station help meteorologists forecast the weather. iStock

Instruments on a weather station help meteorologists forecast the weather. iStock

Each day people who study the weather (they are called meteorologists) tell us what the weather will be like in the place that we live. This is a weather forecast.

In their weather forecast:

  • They tell us what the temperature will be (Hot or cold)

  • They tell if it will be wet (rain) or dry.

  • They tell if there will be clouds or a clear sky.

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These symbols can be used to tell us what the weather will be like:

Can you tell what each one means?

 

 

Watch a video about all kinds of weather

Special clothes keep us dry when the weather is wet. iStock

Special clothes keep us dry when the weather is wet. iStock

Clouds

Clouds are made of tiny droplets of water or frozen ice crystals. You can see clouds floating in the air above the surface of the Earth.

How are clouds formed?

Air contains moisture in the form of a gas which is called water vapour. As water vapour cools it changes from a gas into a liquid. Clouds form when water vapour in the air cools and changes into droplets of water. The tiny water droplets gather together to make a cloud. When the droplets fall, it is rain.

Types of Clouds

The three main kinds of clouds are cirrus, stratus, and cumulus.

Cirrus clouds

Cirrus clouds are white and feathery, and form high up in the sky. They are wispy and thin.

Stratus clouds

Stratus clouds are like flat grey sheets layered across the sky. They are the lowest clouds in the sky, and the drops of water vapour in them are very small. The rain that falls from stratus clouds is drizzle, or snow in very cold areas.

Cumulus clouds are white and fluffy. iStock

Cumulus clouds are white and fluffy. iStock

Cumulus clouds

Cumulus clouds are thick and fluffy, and change shape rapidly.They can be white, or dark when they are full of water droplets and very cold.  

All other clouds are combinations of these three. There are ten types of clouds that are found at different levels of the atmosphere.

Cumulonimbus clouds bring rain. iStock

Cumulonimbus clouds bring rain. iStock

Rain clouds have 'nimbo' or 'nimbus' as part of their name. For example, cumulonimbus are fluffy clouds that bring rain and thunderstorms. They have large drops of rain, and as the temperature gets colder, the drops of rain join together and the cloud becomes dark. They bring lightning, thunder or hail.

Nimbostratus

Nimbostratus are layers of rain cloud. Rain from these clouds falls over a wide area.

The highest of all the clouds are the group of clouds with 'cirrus' as part of their name. They are feathery and white and are made up of frozen water droplets. 

Adding 'alto' to the name of a cloud tells that it is a cloud high in the sky. 

Hail and snow

  • Hail and snow are frozen water.

  • Snow and hail fall from the clouds. 

A large hailstone.

A large hailstone.

What is hail?

Hail is frozen water.

Hail is pieces of ice falling from the sky. Hailstones form in very cold cumulonimbus rain clouds. Most hailstones melt before they reach the ground. Hailstorms are usually short and violent. Sometimes hailstones can be very big, but usually they are very small.

A photograph of snow crystals.

A photograph of snow crystals.

When snow melts it fills dams.

When snow melts it fills dams.

What is snow?

Snow is frozen water. It is made up of tiny, six-sided ice crystals, which form on dust particles inside very cold clouds. The crystals grow in size and join together. They become heavy and drop down through the clouds.

There are many different crystal shapes, but they are always six-sided or have six branches coming out of a central core.

Snow is useful.

Snow is useful because when it melts, the water fills rivers and dams. If it melts slowly, snow doesn't usually cause flooding. But, if it melts quickly snow can cause floods and if rain falls on the melting snow it can make the floods even worse.

Snow is also fun.

People ski on it and play in it.

But, snow can be dangerous.

It can be dangerous for animals when it is very heavy, and difficult for animals to walk through. It covers the food they eat and freezes the water they drink.

It becomes dangerous for traffic when it piles up on the roads.

Snow storms are also called blizzards.  

An avalanche is a large mass of snow that slips down a mountain. People have been killed by avalanches.

Dew hangs from a spider's web.

Dew hangs from a spider's web.

What is dew?

All air contains moisture, which is called water vapour. The moisture in the air close to the ground comes from the soil and the plants. When the air cools during the night, the moisture is cooled and water droplets form on the grass and plants. This is dew.  

We see the dew early in the morning on grass and hanging from spiders' webs.

There is more dew on days when the sky is clear.

When it is cloudy, the trees and plants don't get as cold and there is less moisture to form dew. Dew is dried by the sun's warmth.

What is frost?

Liquid becomes solid when the temperature reaches freezing point, or 0ºC (32ºF). When the temperature falls below freezing point, the moisture in the air freezes into ice crystals and they settle on grass and plants. This is frost.  

Frost can damage plants because it freezes them.

Frost can damage plants because it freezes them.

Frost soon melts and the moisture is dried by the sun.

Frost damages plants because the water inside the cells of a plant freezes and breaks the cells' walls. The frozen parts of the plant will die.  


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