The big low near the North Island is moving closer and deepening, however due to very strong high pressure to the east to south east and south west of New Zealand the rain bands will be weakening and falling apart. For the most part rain will turn to showers (showers being smaller in size and lasting less than 30 minutes generally).

NORTH ISLAND:
Some areas of rain but showers across the northern and eastern half of the North Island, some isolated heavy falls. Mostly dry elsewhere with sunny spells, but some shower activity is possible. Easterly quarter winds. There may be some heavy downpours in the north with a chance of isolated thunderstorms as the centre of the low moves closer to Northland. Some heavier rain or showers possible around the southern portion of the North Island (around Wellington or Wairairapa).
Highs: 11 to 19.

SOUTH ISLAND:
Drizzle or patchy showers moving down the eastern side of the South Island. Sunny on the West Coast for the most part, but cloud towards the north. Easterly quarter winds for many but more southerly for some parts of the west  especially. Showers in Nelson and Marlborough.
Highs: 3 (mainly Queenstown) to 16 (mainly Nelson)

– WeatherWatch.co.nz