Name: Janette L Gubala
What makes it snow?
Snow originates in clouds that are below freezing, but it is not simply frozen
water. The formation of snow requires that dust or other particles be present
in the clouds. Molecules of water vapor adhere directly to the particles,
eventually forming snowflakes. When the snowflakes are heavy enough, they
fall to the ground. As the snowflakes fall through the clouds, sometimes ice
crystals break off the snowflakes; these ice crystals form nucleation points
for more snowflakes, so that one dust particle may be responsible for numerous
Snowflakes are shaped differently depending on temperature, humidity, and
barometric pressure. The larger snowflakes form under high humidity and
relatively high temperatures, since, when the temperature is near freezing or
slightly above freezing, the snowflakes become wet and adhere to one
another. Snowflakes several inches across can be formed in this manner.
The above information is taken from, "It's Raining Frogs and Fishes," by Jerry
Dennis, Harper Perennial, 1993.
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Update: June 2012