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| Earth on Feb 06, 2010

Can it ever be too cold to snow?

No matter how cold a snow-producing cloud is, if it has a source of water, it can build big snowflakes.

It rarely snows when the temperature drops below zero degrees Fahrenheit (-18 degrees Celsius). But snow does sometimes fall even when it’s that cold. Snow can fall even in the coldest place on Earth, Antarctica, at temperatures well below zero.

It turns out that moisture is more important than temperature.

When moist air rises and cools, the water starts to cling to floating particles of dust. If it’s cold enough, the water freezes into the complex ice crystals we call snowflakes. Generally, the colder it gets, the easier it is for snowflakes to form. If there’s enough water, the flakes can get large and the snow can fall.

So it can’t be too cold to snow – but it can be too dry to snow. If it’s too dry, snow crystals may form – but there isn’t enough water left to build large flakes. Any flakes that do form are so small that they evaporate before reaching the ground. The colder it is, the faster all this happens – so it might seem too cold to snow.

No matter how cold a snow-producing cloud is, if it finds a new source of water, it can build big snowflakes again. That’s why Buffalo, New York is known for its snow. No matter how cold it gets there, the clouds can pick up water from nearby Lake Erie to make plenty of snow.