Precipitation
(Water Falling from the Sky)
 There are many different types of precipitation —rain, snow, hail,
and sleet for example—yet they all have a few things in common.
They all come from clouds. They are all forms of water that fall from
the sky. Additionally, they all affect life on Earth, causing some people
to leap with glee while making others scowl, mumbling about umbrellas
or snow shovels, causing garden flowers to grow or causing massive crop
damage.
The most common types of precipitation:
Rain
Drops of liquid water fall from the clouds when water vapor condenses
around dust particles in the clouds, forming tiny droplets that eventually
get too big for the cloud to hold so they fall, growing larger as they
collect more water on their way down.
Snow
Snow is ice that falls from the sky. Each snowflake is a delicately
complex arrangement of ice crystals. A snowflake forms when water vapor
sublimates,
or turns directly from a gas into its solid form, ice.
Hail
Hail is ice that falls from the sky, often in round shapes. Hailstones
form within thunderstorm clouds when upward moving air keeps
pellets of frozen water from falling. The pellets grow larger as
drops of very
cold water hit them and freeze. Eventually the balls of ice become
so large and heavy that they fall to the ground as hailstones.
The largest
documented hailstone weighted more than one and a half pounds!
Scientists estimate that it reached a speed of more than 80 mph as
it fell toward
Earth.
Sleet
Sleet is like slush falling from the sky. Sleet forms when raindrops
freeze into ice as they fall to the ground. They are usually
smaller and wetter than hailstones.
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