A strong cold southerly airflow over the South Island spreads over the North Island today bringing rain with a risk of heavy falls and hail. Also some snow about the Central Plateau.

Northland, Auckland, Waikato & Bay Of Plenty
Showers and sunny spells, showers may be heavy late afternoon / evening with hail. Breezy westerly winds change southerly later in the day then showers ease overnight. The Bay Of Plenty stays mostly sunny till showers arrive late afternoon.
Highs: 12-14

Western North Island (including Central North Island)
Rain with a chance of heavy falls and hail, spreading into Taranaki around midday then easing late afternoon or evening to a few showers. Snow lowers to 400m about the Central North Island by evening however at that point flurries will have eased also and become fairly infrequent. Fresh cold southerly winds, strong about the coast.
Highs: 5-13

Eastern North Island
Rain about the Wairarapa spreads into Hawkes Bay during the afternoon then Gisborne by evening along with a fresh cold southwest change. Rain may be heavy with a risk of hail. Some snow falls to 400m. Conditions before rain moves in will be mostly sunny with light winds.
Highs: 10-14

Wellington
Morning rain (possibly heavy with hail) then easing to the odd infrequent shower, showers pick up again overnight. Snow to 400m. Strong southerly winds.
High: 10

Marlborough & Nelson
Morning rain (possibly heavy with hail) with snow to 400m then clearing, areas of sun break through from afternoon, fresh cold southwesterly winds.
Highs: 9-11

Canterbury
Early rain (widespread) eases to showers which are then mostly coastal, some sun may break through, mainly inland. Showers picking up again from afternoon and perhaps drifting back inland for a time. Showers may be heavy at times with hail, snow flurries to 200m then lifting overnight at which point some rain moves through. Cold southwesterly winds, strong about the coast.
Highs: 6-7

West Coast
Any early showers clear then mostly sunny weather develops by midday, south to southeasterly winds. Overnight or perhaps more towards dawn on Thursday there may be some rain for a time.
Highs: 8-10

Southland & Otago
Showers, possibly heavy in the morning with small hail then easing. Snow flurries to low levels (200 to 100m) in the morning also then gradually lifting from afternoon. Overnight some rain moves through for a time. Cold southwesterly winds, strong about the Otago coastline.
Highs: 6-9

By Weather Analyst Aaron Wilkinson – WeatherWatch.co.nz