Looking to travel to AU/NZ in July/August...any tips for winter travel?

I am going to have some free time off in July/August so I am thinking of taking a trip somewhere for a few weeks around that time. My first idea was to go back to the South Pacific as I studied in Australia when I was in college. I would love to go skiing in NZ and check out some of the places I missed in Australia (Uluru, Great Barrier Reef)

But I am worried that winter might not be the best time to go. I visited NZ when I was studying abroad and was blown away by its beauty and would have loved to go hiking and visit some of the national parks, but I don't want it to be too cold to do those sorts of things. I don't really know what the winter is like so I'm a little hesitant about this being a good idea and maybe it would be best to choose somewhere I haven't already been.