|MadSci Network: Earth Sciences|
Snow occurs when moisture in the air condenses into ice crystals. This can take place as long as the temperature of the layer in which condensation is occurring is below freezing. Besides moisture, the other requirement is a source of lift to aid in the condensation process.
Therefore the answer is no, it can't be too cold to snow. However the colder the air is, the less moisture it is capable of holding. As a result, heavier snowfalls generally ocurr in relatively warmer (but still below freezing) air.
In extremely cold air, moisture can condense out much easier (without the lift necessary to produce clouds). In these cases, crystallization can occur, and the ice crystals can fall from the sky even when no clouds are present.
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