mermaidnz lives in NZ...send her a PM. I'll bet she can give you a good weather report.
However, I hear a lot will depend on where you go. There was a weeklong hike in NZ I read about a few years ago, where you go through like all the different topographies in the world (rain forest, savannah, desert, etc.) except one. So, sounds like there will be some temperature variations...
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"Life is not measured in the number of breaths we take, but by the places that take our breath away..."