Snow
Snowflakes form when water
vapor freezes into ice crystals in cold clouds. The ice crystals attract
cooled water droplets to form various shapes. They get heavy and fall.
If the air is cold enough, the snow falls all the way to the earth
without melting. If the ground is freezing, the snowflakes stick to
the ground.
Go
here to see how air temperature creates other kinds of precipitation
No
Two Alike?
Have you noticed that there
are many different shapes of snowflakes? That is because a snowflake
is usually made of many different kinds of snow crystals, and the shape
of a snow crystal depends a lot on the temperature at which it forms.
For example, at temperatures from 25 to 32 degrees F, the crystals
are shaped like thin plates. At temperatures between 20 and 25 degrees
F they look more like needles and at 15-20 degrees F they resemble
hollow columns. The general rule is the colder the temperature, the
smaller the crystals.
As the crystals fall from the cold clouds, they bump into other crystals and
freeze together, making even more shapes. This is one reason why it's so
hard to have two snowflakes exactly alike. In fact, in air right at the
freezing mark, several snowflakes may stick together, forming large clumps
of flakes that may melt as they hit the ground.
Fun
Facts
- Almost every place
in the United States has seen snow. Only the Florida Keys has remained
flurry-free.
- The most snow ever
to fall in one winter was at Mount Baker in Washington State. In
the winter of 1998-1999, 1, 140 inches fell, almost the height of
the Statue of Liberty from head to toe.
- Rochester New
York is the snowiest large city in the United States,
averaging 94 inches of snow every year.
More snow falls each year in southern Canada and the northern U.S. than at
the North Pole!
- Depending on air
temperature, the same amount of moisture in one inch of
rain could equal anywhere from two inches of wet slushy snow to
as much as 40 inches of dry fluffy snow.
