nah it only snows on the mountains during winter,
you get the occasional storm in the citys, but most of the time its only way up on top.
as for the skiing down there....
im from the north island ski fields, so il try to give you my most honest answer, ( bit a rivalry )
um there okay... they get beta snow (lighter and Dryer) but we have got defently better terrain up north, if i was heading to NZ id spent winter ( july august ) down south island and then move up north island for the spring ( septmeber, october, november)