Weather: Winter to bite next week with icy air pushing temperatures down, snow across South Island

Parts of New Zealand may have recorded their coldest night of the year this week but winter is just getting started, according to the latest forecasts.

MetService said on Thursday that clear skies and light winds over the North Island meant some areas had experienced their chilliest nights of the year. At 7am on Thursday, Hamilton sat at -2C, Rotorua was at -1C and Taupo was at 1C.

But that may just be the start of winter's wrath, with Ben Noll, a meteorologist at NIWA, telling The AM Show on Friday that things will move up a gear next week.

"If June ended today, it would actually be New Zealand's warmest June on record. Hard to believe," he said. "The first two weeks of the month were pretty warm. The last week or so has been a little bit more variable, but overall, we have certainly set ourselves pretty high up the list here. But that is all about to change."

He said a polar jet stream is pushing air from the Antarctic ice sheet north, meaning temperatures will dive and snow is likely across southern parts. 

"It's in the southern ocean, it's coming our way as we go into next week. So some good news for those South Island ski fields looking ahead to Monday. I wouldn't be surprised to see some flurries down to sea level potentially, Southland and Otago on Monday as well."

He said inland alpine parts of the South Island may get down to -10C, while Auckland could fall to around 0C. On Thursday, MetService recorded Auckland Airport at 4C.

Weatherwatch's Philip Duncan agreed after a warmer than average weekend, things will get chilly.

"A southerly will move in on Monday and Tuesday from the polar region and will dramatically cut back daytime highs, especially in the south and east of both main islands."

There's also more rain on the way.

"We will see that snow next week and then that will clear away, it will be dry and then the rain will return during the first week of July," Noll said.

He told The AM Show unusually warm waters in the western Pacific Ocean are prime ground for moisture, which can flow down to New Zealand - like what caused the Canterbury floods earlier this month. 

"As we go through the next couple of weeks to months, that was an atmospheric river event, so this plume of moisture coming down from the tropics. There might be a few more of those as we go through the rest of the winter season."