The weather in New Zealand is fickle. You can experience the four seasons in one day in most locations. And so you need to be mindful of this, especially if you intend to spend any time tramping (walking in the bush) or climbing or sailing or mountain biking or camping or...
The Victoria University of Wellington Weather Service provides a comprehensive overview of satellite imagery, ocean weather, forecast charts and the current weather in terms of temperature, precipitation, pressure and wind.
For a simpler version, the weather, as it is right now, is shown below. Just click each "magnet" for a 10-day forecast...