Weather: 'Unusual warmth' for New Zealand but frost risk for South Island

New Zealand is set to swing from storms to "unusual warmth" this week as active weather eases across the country. It could mean shorts weather again for the North Island - while the South might need the long johns at night.

"On Wednesday low pressure to the north will drive in more nor'easters, keeping it mild for this time of the year in the North Island,"  WeatherWatch CEO and head forecaster Philip Duncan​ says on YouTube.

"But the South Island, more under high pressure, that's where even some frosts are possible - certainly getting down into the lower single digits overnight tonight and into Wednesday morning."

A NIWA wind and temperature graphic for the week shows a respite for the country after torrential rain in Canterbury and a large storm off the eastern seaboard of the North Island.

"Over the next several days, unusual warmth (for the time of year), will have a firm grip on Aotearoa New Zealand," NIWA says.

"Note the lack of southerlies over the NZ region."

By Thursday New Zealand will be in between high pressure as the nor'easters continue coming into northern New Zealand, and by Friday high pressure balloons out across the country.

"It's mild though for this time of the year in northern New Zealand, elsewhere colder by night with the light winds and clear skies," Duncan says.

High pressure continues building up on Saturday leading to a "pretty settled weekend".

"A couple of isolated showers are possible otherwise not much going on by Sunday," Duncan adds.

"High pressure is out to the east and now we've got this mild northerly flow coming down and that means rain returns on Sunday over to the West Coast and probably by Monday it will start to move into northern areas."