"Wow," said Ron, when Harry had finally finished telling them everything; Ron was waving his wand very vaguely in the direction of the ceiling without paying the slightest bit of attention to what he was doing. "Wow. You're actually going with Dumbledore... and try and destroy... wow."
"Ron, you're making it snow," said Hermione patiently, grabbing his wrist and redirecting his wand away from the ceiling from which, sure enough, large white flakes had started to fall.
Enchanted snow is warm and dry, usually used for decorative purposes.
A magical imitation snow which, unlike real snow, is warm and dry.