PRECIPITATIONUnit 2: Weather

WHAT IS PRECIPITATION?

When water falls to Earth, it is called precipitation. Rain, snow, sleet, and hail are all forms of precipitation.

HOW IS RAIN FORMED?

For rain to fall, the water drops in a cloud must reach a certain size. As the tiny droplets of water in a cloud bump into each other, they combine.

When the drops are heavy enough, they fall as rain.

HOW IS SNOW FORMED?

If the air is very cold, water vapor in a cloud may freeze into tiny ice crystals called snow. All snowflakes have six sides, or points.

HOW IS HAIL FORMED?

Hail may fall during a thunderstorm in the spring or summer. Hail begins as tiny pieces of ice in a thundercloud.

1st- The piece of ice start to fall, but they are swept back up by a current of air.

2nd- As the pieces fall again, they collect more water.

3rd- This water freezes, making the hail larger. This happens over and over again until its so heavy it falls to the

ground.

DEW AND FROST

Sometimes you will find that blades of grass have drips of water on them even when it has not rained. This water is called dew.

Dew forms when there is a large amount of water vapor in the air.

1st- At night, the air cools off.

2nd- Cool air cannot hold as much moisture as warm air, so the water vapor forms into drops of dew.

3rd- If the ground is very cold, the dew freezes and forms frost.