A northwesterly airflow lies over New Zealand today with a cold front approaching the lower South Island from the southwest, this moves onto the lower North Island later today / overnight.

Northland, Auckland, Waikato & Bay Of Plenty
Mostly sunny, there may be some early fog then clearing. Cloud builds in the afternoon bringing the risk of an isolated shower, clearing evening. Light north to northwesterly winds.
Highs: 17-18

Western North Island (including Central North Island)
Partly cloudy skies, risk of a morning shower then clearing. Freshening northwesterly winds.
Highs: 14-16

Eastern North Island
Sunny and warm, light northwesterlies for most, a bit breezier for Wairarapa.
Highs: 18-21

Wellington
Cloudy areas, brisk to strong northwesterly winds rising to gale at times especially through Cook Strait.
High: 15

Marlborough & Nelson
Sunny with some high cloud from afternoon, overnight spots of rain possible. Northerlies for Nelson, northwesterlies become gusty in the afternoon for Marlborough.
Highs: 17-21

Canterbury
Mostly sunny with developing high cloud, rain moves into the high country later in the evening / overnight. North to northwesterly winds pick up in the afternoon.
Highs: 18-22

West Coast
Mostly cloudy, showers about Fiordland turning to rain in the morning then becoming heavy in the afternoon. Showers move northwards reaching into North Westland during the afternoon then turning to rain later in the day, becoming heavy overnight. North to northeasterly winds freshen.
Highs: 12-14

Southland & Otago
Thickening high cloud, evening rain about Southland and Central Otago (especially in the west). Overnight spots of rain for Coastal Otago. Breezy north to northwesterly winds.
Highs: 18-20

By Weather Analyst Aaron Wilkinson – WeatherWatch.co.nz