Is it ever too cold to snow?
No, it can never be too cold to snow. However, the amount of water vapor in the air diminishes greatly as temperatures fall and at readings below zero, heavy snow is just about impossible because moisture is so limited.
All that is required for snow to occur is the presence of water vapor in the air and a mechanism to chill the air below its saturation temperature. Water vapor will condense out of the air when that happens, forming ice crystals if the temperature is below freezing.
Consider Antarctica. On May 18, 1972, at the South Pole Station, with a high of 57 below zero and a low of 76 below, one-tenth of an inch of snow occurred. Not much snow, but snow nonetheless. That information comes to us from Edward Jessup, retired now, but then Meteorologist in Charge of the South Pole Station.