Hailstorm Valkyrie

Snow isn't a type of mana. If an effect says you may spend mana as though it were any type, you can't pay for {S} using mana that wasn't produced by a snow source.

Snow is a supertype, not a card type. It has no rules meaning or function by itself, but spells and abilities may refer to it.

Some cards have additional effects for each {S} spent to cast them. You can cast these spells even if you don't spend any snow mana to cast them; their additional effects simply won't do anything.