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Dear Tom,
We have all heard the old saying, “It’s too cold to snow.” This isn’t true, is it?

Jerry Johns, Chicago

Dear Jerry,
Nope. In the Earth’s atmosphere, it can never be too cold to snow. All that is necessary is water vapor in the air–and some is always present, even at very low temperatures–and a mechanism to chill the air below its saturation temperature. Antarctica satisfies both conditions and the icecap is dramatic proof that snow falls there in frigid temperatures.

Direct observation confirms it. Ice crystals and light snow have been observed at the South Pole Station with temperatures at 70 below zero. Even Chicago has simultaneously experienced snow and bitter cold. On Jan. 10, 1982, 0.8 inch of snow was observed at Midway Airport while the temperature was 15 degrees below zero.

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