Ask A Met: Is It Ever Too Cold To Snow?

This week’s question comes from Morning Brief reader Robynn who asks, “Is it ever too cold to snow?”

Meteorologist Jonathan Belles: This might sound like a myth, but I have two answers to this question.

First off, theoretically, it is not possible for it to be too cold for snow. You could grow snow near absolute zero in a lab, if you could actually control the conditions to get it to that point.

On the other hand, realistically, I think our northern readers would know that, yes, it gets so cold sometimes that it will likely not snow.

Let’s just talk about one example. If you look at Antarctica, you’ll see that it is actually one of the largest deserts on Earth, because it doesn't really snow.

The snow that comes down there is fairly rare, and it is so cold down there most of the year that it's not the snowflakes that come down. They’re very small grains of ice, almost like mist particles that come down. People wouldn't really think of it as snow.

Once you get kind of below 0 degrees, it gets substantially harder to get the kind of snow that you see in a Hallmark movie: big, fluffy snowflakes and that sort of thing. You get more or less grainy stuff: pellets, the kind of nasty, yucky kind of stuff.

The reason for that isn't necessarily the cold; it's actually the moisture. That’s because the colder the air is, the less moisture it can hold. Without moisture, there is no snow.

The converse of that is true, too. Warmer air can hold more moisture.

There's a zone in the atmosphere, roughly 12 to 19°C below zero, where snowflakes tend to grow. That is like the sweet spot where you get those arms and the branches on the snowflakes to grow. It's called the Dendritic Growth Zone.

Just try to say that three times fast.

Do you have a question to ask the meteorologists at Weather.com? Write to us at [email protected] and we’ll pick a new question each week from readers to answer.