Never Go During Peak Season
Source: https://www.queenstownnz.co.nz
Just like Australia, New Zealand has their summertime during December through February, and their winter from June to August. And since many tourists like to get away from the cold winter months in their own countries, they tend to visit New Zealand to enjoy the much warmer weather. Just know that when you during these peak months, things are going to be more expensive than usual. So if you are on a tighter budget, it would probably be best to go during another time of the year.