Is it ever too cold to snow? That's the question in this Moment of Science.

Meteorologists who have looked at the records tell us that it's never too cold to snow. Snowfall has been observed at temperatures as low as 53 degrees below zero Fahrenheit. There are several reasons we might not associate snowfall with very cold weather.

First, cold air holds less water vapor than warm air. Snowflakes ultimately need water vapor to form; therefore, the less vapor, the fewer flakes. Nevertheless, there is always at least some water vapor available, no matter how cold the air gets. And under the right conditions, that vapor might produce clouds and snow.

Another reason we tend not to associate snowfall with very cold weather is that, here in the United States at least, the coldest weather tends to occur in strong high-pressure areas without clouds.

In particular, we may tend to associate the deepest cold with crystal-clear nights. Clear nights feel especially cold partly because our body heat is lost directly to interplanetary space. Every warm object, including the surface of the earth and every human being, releases heat energy in the form of invisible infrared light. On a clear night, that infrared light goes off into space, never to return.  Clouds, if they're present, reflect some of that infrared light back to the ground and to us. When the infrared light hits our skin, some of its energy is converted back to heat, which makes us feel a little warmer than we would under a clear sky.

So it's never too cold to snow. But snow and extreme cold don't usually go together because the coldest nights are usually clear nights.

More like this:

• Benjamin Franklin and his fabric swatches in the snow
• A world without snow
• Dinosaurs in the snow

This episode is an adaptation of a broadcast featured in the book Why You Can Never Get to the End of the Rainbow and Other Moments of Science, published by Indiana University press, and edited by producer Don Glass.