A few unexpected snowfalls could be a fluke but my guess is that climatological instability is at fault--and this is partly due to global warming. We had the hottest July on record where I live. And the '00s that just went by was the hottest decade in recorded history. Having said that, most climate change is predicted to be gradual (over years), although some scientists believe that global warming will escalate at a very steady rate (which we have seen lately). If it happens too fast, we may end up in an ice age due to how currents can react to overheating. And afaik it takes only 2-3 weeks for an ice age to actually set in on the world
So we don't really know whether we're in for a deep burn or a deep freeze, but in either case we're not headed in the most comfortable direction. A few snowflakes in New Zealand doesn't make me think "oh no, an ice age". Sometimes a fluke is just a fluke.