A northwesterly airflow lies over New Zealand today, meanwhile a cold front / southwest change pushes northwards over the South Island during the day.

Northland, Auckland, Waikato & Bay Of Plenty
Sunny spells, chance of a shower from afternoon mainly about Northland and the Waikato (especially in the west). West to northwesterly winds.
Highs: 16-17

Western North Island (including Central North Island)
Cloudy areas with a shower or two possible at times, more so from late morning. Northwesterly winds.
Highs: 15-16

Eastern North Island
Sunny with some high cloud, mainly later. Northwesterly winds.
Highs: 19-21

Wellington
Mostly cloudy, a few spits possible from afternoon (mainly in the north). Widespread rain overnight. Strong northwesterly winds.
High: 14

Marlborough & Nelson
Plenty of high cloud, a few showers develop about Nelson in the afternoon. Rain moves in later in the evening becoming widespread. North to northwesterly winds.
Highs: 16-18

Canterbury
High cloud, southerlies pick up late morning about South Canterbury moving into North Canterbury this afternoon bringing some rain.
Highs: 16-17

West Coast
Showers, heavy rain about South Westland spreads into North Westland by midday then easing back to showers in the evening. Northwesterly winds change southwest in the afternoon.
Highs: 11-13

Southland & Otago
Occasional showers for Southland, clearing in the evening. Some sun may break through at times. Otago sees morning rain easing to showers, sun breaks through at times from afternoon. Southwesterlies die out later in the day.
Highs: 10-13

By Weather Analyst Aaron Wilkinson – WeatherWatch.co.nz