I did NZ with JY a few years ago and I went in January, the weather and climate was fine in that month, it a great tour, you will have fun.
I Have been to Australia independently as unfortunately my tour date was cancelled, I went in June 2007 the weather was good. I did a very similar itinerary as the JY tour. I must say that of all the tours I have done Australia is my most favourite holiday I loved the country and the people.
Any questions just ask...
Cindy