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Why does it snow?

Published on
17 January 2011

monarda frost small 225x300Do you ever wonder why it snows?

With the regular snow events that we’ve had since early December, I find myself thinking about snow – where it comes from and why it falls…

Well, the simple explanation is that we get snow when moisture falls from the clouds and the air is below freezing, so the water falls in a frozen state.

Actually, it is so cold up in the clouds that all rain starts out as snow, but then it thaws on the way down.

According to a short article on The Weather Predictor website, ice crystals form in clouds, and as they stick to each other, eventually they become heavy enough that they fall.

If the air is warm enough on the way down, the ice crystals (aka snow flakes) turn into rain drops. If the air temperature is just above freezing, the snowflakes partly melt and we get sleet. And if the air is below freezing, then we get snow!

Now, snow takes up a lot more space than rain. In fact, on average, a 10″ snow fall, if melted, would yield about an inch of water. So, when we get a couple inches of snow, and traffic gets all messed up — cars in the ditch, skidding on the slick pavement — that is an amount of water equivalent to less than a quarter inch of rain.