A south to southwesterly airflow lies over New Zealand today, a cold upper pool of air in this flow moves over the North Island and this will result in some instability this afternoon.

Northland, Auckland, Waikato & Bay Of Plenty
Partly cloudy, a mainly dry morning although there may be a coastal shower. Isolated showers develop for most in the afternoon, some could become heavy with thunderstorms then easing later. Light winds tend onshore.
Highs: 22-25

Western North Island (including Central North Island)
Mostly cloudy with showers or perhaps some rain, southerly winds, gusty about the coast tend southeast in the evening then drying out.
Highs: 18-19

Eastern North Island
Some rain south of about Napier, easing to showers in the afternoon. In the afternoon showers spread north of Napier after a dry start. Showers may become heavy with thunderstorms about the ranges of Hawkes Bay and Gisborne this afternoon then easing later on. Southwesterly winds.
Highs: 18-23

Wellington
Showers or some rain, easing evening. Strong southerlies with gales through Cook Strait, easing at night.
Highs: 16-17

Marlborough & Nelson
Partly cloudy, a shower or two for Tasman, perhaps Nelson. Southwesterly winds.
Highs: 19-21

Canterbury
Showers, some rain for the Kaikoura area, clearing later. South Canterbury is dry with sun, perhaps some sun later in the day for Mid and North Canterbury. South to southwesterly winds.
Highs: 18-23

West Coast
Mostly sunny with some high cloud in the north, southeasterlies tend northwest in the afternoon.
Highs: 23-25

Southland & Otago
A mix of sun and cloud with southerly winds.
Highs: 19-23