Larry Bartlett, age 11, of Montreal, Quebec, Canada, for his question:

Is it ever too cold to snow?

We often hear that the weather is too cold for snow. This may be so, because the atmosphere needs moisture to form snowflakes and cold air tends to be dry. This is because warm air can hold more gaseous water vapor. As it chills, its surplus vapor is converted to liquid droplets of mist or to frozen ice crystals. Air that has been very cool for a long time has lost most of its moisture, in which case it may be unable to form snowflakes.

This is a good theory. But the evidence suggests that even the coldest air can produce a few rather hard little snowflakes. In Alaska, snow has been recorded when the temperature was 52 degrees below zero. At the South Pole, temperatures often dip lower than 100 below, yet snow can occur at any time. In Antarctica, no month has a mean average tem¬perature above freezing. Yet the ice bound continent accumulates an estimated 300 cubic miles of surplus snow every year. Obviously the earth's atmosphere never gets too chilly to shed a little snow.