Sometimes, during cold weather, it snows – but other times, it’s just so cold that it’s too cold even for snow.
Anyone who’s lived in a country where it snows in winter will recognise the feeling behind this popular piece of folk meteorology: there are days when the cold is so intense, you have the sense that even the snow is too frozen to fall. “It’s been trying to snow all day,” people will say, “but it’s just too cold.” Professional meteorologists, however, say that nowhere on Earth can ever be literally too cold for snow; it can and does snow at extremely low temperatures. But it is true that snow is less common and less plentiful once ground level air temperatures get much below zero (the figure given varies), mainly because of a lack of water vapour in the cold air. Even then, signifi cant snowfall can occur under certain circumstances, such as up a mountain, or over a source of heat or body of water. Snow is certainly not unknown, for instance, at the frozen Poles. Only at absolute zero (–459oF or –273oC), say the experts, would snow become impossible. Along with everything else.