It can be too cold to snow.
Don’t Believe That!
It can obviously be too warm to snow, but an expression commonly heard this time of year is that it can also be “too cold to snow.”
The formation of snow requires moisture in the air, the proper temperature (too high and we’ll get rain instead) and the appropriate environmental conditions for snowflakes to develop in the atmosphere before falling to the ground (else we might get hail or sleet or nothing at all).
At lower temperatures, air becomes dryer – that is, it can hold less water vapor. This decreases the likelihood and amount of snow as the mercury drops. The myth of it being too cold to snow may have originated from this valid scientific concept, but it was taken to an (incorrect) extreme. No matter how cold it gets, the probability of snow is never zero. In addition, temperatures at higher altitudes can sometimes be significantly warmer than the surface temperature. Thus, this warmer air can still produce a significant snowfall.
Bonus Fact #1: Snow has been recorded in Antarctica, at 70 degrees below zero (Fahrenheit).
Bonus Fact #2: The main difference between snow and hail is that hail is frozen raindrops whereas snowflakes are formed when water vapor freezes without first going through the liquid phase. Sleet is small ice pellets that are created when snowflakes liquefy, then freeze again, by passing through different air temperature layers on the way down.