2003 Flight Forecast

2003 Flight Forecast

Cloud Clues

[What Are Clouds?] [Types of Clouds] [Online Activity]

Pilots need accurate weather reports to make air travel safe and comfortable for their passengers. Certain types of weather conditions can put a plane and its passengers in danger. Very high winds and severe thunderstorms are some examples of weather conditions that make air travel unsafe. Sometimes a plane does not takeoff at its scheduled time because of poor weather conditions. This weather delay happens because it is very important to pilots and airlines that their passengers are kept safe!

Airlines and pilots rely on weather forecasters (called meteorologists) to tell them what kind of weather to expect. They talk to these aviation weather forecasters and flight dispatchers to find out about weather conditions en route and at their destination. They use the information to choose a route, altitude, and speed for a safe, smooth flight. But they can also look to the sky for clues from nature's road map! Clouds can send us messages about the weather if we know how to read them.


Heat from the sun causes water on earth from rivers, lakes or oceans to go into the air and change into a gas called water vapor. This is called evaporation.

Clouds are formed from warm air that rises from the earth carrying water vapor in it. The water vapor cools as the warm air rises higher. When it cools it changes into droplets of water (or crystals of ice.) Clouds form when these droplets of water collect around small bits of dust, sea salt or pollution floating in the air. The word for this is condensation.

The droplets bump into each other and get bigger and bigger. When the water droplets become too heavy to stay in the air they fall to the ground as rain or snow. Another word for rain or snow is precipitation. Some of this precipitation will collect into the rivers, lakes and oceans on earth and start the cycle all over again!


Some clouds are so low they touch the ground, while others are high in the sky. Clouds come in many shapes. Pilots can predict the weather just by watching the clouds and the direction they are moving in. Clouds can give them messages about what the weather will be like many hours in advance. Just by studying a cloud's shape they can tell a great deal about the cloud.

There are three basic kinds of clouds.

Cirrus Clouds

Cirrus clouds are thin with fuzzy edges that look like feathers. They are high in the sky. They are so high that they are made up of ice particles. The winds that are high in the sky are often different from the winds direction on the ground. If the cirrus clouds are moving from right to left (high pressure) the weather will be warmer. If the cirrus clouds are moving from left to right (low pressure) on a summer day colder weather with rain may be coming.

Cumulus Clouds


Cumulus clouds look like puffs of cotton with flat bottoms piled in a heap. They are usually nearer the earth than cirrus clouds. Cumulus clouds puffy and white mean fair weather will continue. Cumulus clouds that stack up, turn dark gray and grow taller early in the day can turn into thunderstorms later.

The word NIMBUS added to a clouds name means that rain or snow is falling from the cloud.

Cumulonimbus clouds are the thunder clouds that bring strong winds, hail and rain on a summer day. They are a type of cumulus cloud.

Stratus Clouds

Stratus clouds are low, flat sheets of clouds that are the lowest clouds in the sky. They are often dark and can bring long lasting rain or snow flurries. When stratus clouds are close to the ground they are called fog. These clouds can create poor visibility for pilots. Stratus clouds can stay in one place for several days. These clouds can stretch for hundreds of miles!

Now that you have learned more about clouds and the messages they send us,
try the Cloud Clues Activity to test what you know!

HINT: You might want to write down the names of the three types
of clouds before you take the test.

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National Science Education Content Standards
[K-4] Content Standard B: Properties of objects and materials.
[K-4] Content Standard D: Objects in the sky; Changes in earth and sky.
[K-4] Content Standard F: Changes in environments.
[K-4] Content Standard G: Science as a human endeavor.

[5-8] Content Standard B: Transfer of energy.
[5-8] Content Standard D: Structure of the earth system.
[5-8] Content Standard F: Natural Hazards.
[5-8] Content Standard G: Science as a human endeavor.

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