Wrap up warm as year's coldest fortnight begins

Temperatures at Mt Cook dropped to -8.2 overnight.

It was a crisp, sunny day for most of the South Island today after overnight temperatures plunged well below freezing in inland areas.

And tomorrow it's only set to get colder, with Niwa warning the risk of frost will cover almost the entire South Island and the lower half of the North Island tomorrow morning.

Further north there were showers on and off all day today, with MetService forecasting the rain would set in this evening.

That doesn't bode well for tomorrow's America's Cup parade in Auckland. The MetService is forecasting periods of rain, possibly heavy at times, along with northwesterly winds for the city.

Parts of the South Island dropped below zero last night, some to as low as -8.2C.

Frost risk Thursday morning compared to today.

Note how the white area expands --> higher risk for frost tomorrow!

Be safe on the roads. pic.twitter.com/C1aV3d7BtR

— NIWA Weather (@NiwaWeather) July 5, 2017

Temperatures at Mt Cook airport between 4 and 5am dropped to -8.2C, to -5.3C at Tekapo, -4C at Pukaki Airport and -3.2C at Alexandra.

In the lower North Island, temperatures dropped to -3.4C in Masterton, -3.5C on the Desert Rd, -2.3C in Upper Hutt and -1C in Martinborough.

Cold out there! At 7am, Tekapo -6C, Alex -4C, Masterton -3C, Wanaka -2C. Desert Rd dipped to -4.5C earlier #brrr https://t.co/oKYtro2Yts ^GG

— MetService (@MetService) July 4, 2017

Temperatures in most of New Zealand are forecast to be colder than usual during what is the chilliest time of the year.

The MetService long-range forecast is picking below-average temperatures for the first half of this month.

MetService meteorologist Georgina Griffiths said this is "typically the coldest fortnight of the year".

"All indications are that most of New Zealand will see below-average temperatures during this time."

Recent snowfall over the lower South Island will be welcome news for those planning ski trips during the school holidays, "but it's a different story for the power bill" Griffiths said.

Icy conditions have also led to warnings and closures on SH90 from Raes Junction to Willowbank, and on SH80 from Aoraki Mt Cook to Ben Ohau, were drivers are advised to take extra care because of snow and ice.

SH1 from Hundalee to Kaikoura is closed because of slips.

The frozen temperatures are also affecting public transport. The Hutt Valley Line train has been delayed for 15 minutes because of ice on the overhead powerlines.

HVL: The 6.40am service from UPPE to WELL has departed UPPE 15 minutes late due to ice on the overhead powerlines

— Metlink Wellington (@metlinkwgtn) July 4, 2017

The north of New Zealand, from Northland to Waikato, including the Coromandel Peninsula, will have scattered showers turning to rain this evening.

Bay of Plenty will be fine during the day with scattered rain tonight.

Gisborne, Hawke's Bay, and Waitomo to Kapiti including the central high country will be fine.

Wairarapa and Wellington will have isolated coastal showers later in the day and Marlborough and Nelson will be waking up to morning frosts or fog.

Buller and Westland will have spots of frost and fog while Canterbury will be mainly fine, apart from showers near Banks Peninsula.

There will be a few showers along the Otago coast this evening but Otago, Southland and Fiordland will be mainly fine.

- Additional reporting: NZN