Hi Nat,
Don't have any personal experience of Auckland's weather apart from passing swiftly through on the way to and from the airport but I gather it's generally mild with a fair amount of rain and humidity.
Here's a few sites to read up about NZ weather in general.
National Climate Centre
Met Service
Metvuw Some great photos of cloud formations and sunsets
Weatherbase This gives a view of average temperature and rainfall for Auckland.