A small low pressure system today develops a little further off the West Coast, moving into the South Island tonight and falling apart. High pressure remains to the north east of NZ and there is a squash zone of air pressure (an area with windy conditions) over the upper South Island/Central NZ/lower North Island.

NORTH ISLAND:
Mostly Sunny in the east, cloudy areas in the western side. Warmer than average for many areas this afternoon, especially in the east. NW winds becoming blustery in exposed parts of the lower North Island. Dry or mostly dry across the island. Cloudy later in the west.
Highs: 14 to 20

SOUTH ISLAND:
Heavy rain slowly moves up the West Coast, not clearing until tomorrow but a mix of sun and cloud in the east. Dry or mainly dry elsewhere although rain develops later in Nelson (mostly likely at night) and some patchy light rain or drizzle may spread across some parts of Southland and Otago (spilling over from the west). A cooler change south of Banks Peninsula, especially in coastal areas of the east.
Highs: 11 to 19

– WeatherWatch.co.nz