Summers start in October/November but being a maritime climate the weather can be changeable. The weather in January - March is a little more settled.
Winter can be harsh and snowy, keep this in mind when planning your travel. The general snow season is about early June until early October in the South Island, and snow does happens in the /central North Island but less frequently. Gloves, scarf and hat are definitely a good idea if your thumb brings you up in the mountains.
== Other travelling infos ==