A cold front moves off the upper South Island this morning then onto the North Island this afternoon with southwesterly winds strengthening in behind. Meanwhile a second even colder front moves northwards over the South Island today bringing a chance of sea level snow in the south and east.

Northland, Auckland, Waikato & Bay Of Plenty
Some cloud, the odd shower in the west, westerly winds. A gusty southwest change in the afternoon brings rain, easing to showers in the evening. Bay Of Plenty dries out in the evening after rain clears.
Highs: 15-17

Western North Island (including Central North Island)
Some cloud, the odd shower. Rain develops around midday as northwesterlies change southwest, snow lowers to 700m. Clearing up in the evening for a time then around midnight expect further showers as winds change southerly, snow lowers to 400m.
Highs: 8-15

Eastern North Island
Sun / high cloud, late morning rain moves through Wairarapa then further north during the afternoon as northwesterlies change southwest. Clearing up for a time in the evening then overnight showers push northwards again bringing a dusting of snow to the ranges as southwesterlies strengthen, 200m in the south, 400m in the north.
Highs: 14-20

Wellington
A mix of sun and cloud, risk of a spit. Late morning northwesterlies change gusty southerly bringing rain, clearing up late afternoon for a time then rain moves back in later in the evening. Snow lowers to 400m in the afternoon, 200 to 100m overnight.
Highs: 12-13

Marlborough & Nelson
Rain develops about Nelson in the morning then spreading over into Marlborough around midday as southwesterlies freshen. Clearing up in the afternoon, sun may break through. A further period of showers in the evening possibly heavy with small hail (more so for Marlborough). Snow to 600m around midday, 300m later in the evening. Southwesterly winds.
Highs: 12-14

Canterbury
Rain with snow to 400m, clearing up in the afternoon. Late afternoon showers move back in possibly heavy with small hail (maybe some thunder), snow lowers to near or potentially to sea level later in the evening at which point showers clear away from inland areas and South Canterbury. Southwesterlies strengthen later in the day with gales about the coast.
Highs: 8-10

West Coast
Rain, easing to showers in the afternoon, clearing about South Westland late afternoon then further north later in the evening / overnight as southwesterlies change southeast. There will be snow in the ranges to about 400m, 300 to 200m for Fiordland, snow lowers in the evening a bit more before clearing.
Highs: 11-14

Southland & Otago
Rain, small hail and snow to 300m, lowering to sea level in the afternoon with a chance of thunder, perhaps not to sea level for Otago till evening. Parts of Invercargill may see snow avoid the city, a little touch and go due to the sheltering of Stewart Island. Southwesterlies strengthen in the morning for Southland then afternoon for Otago.
Highs: 5-8