Temperatures plummet to zero as icy blast dumps snow on North Island

A cold snap sweeping across the country has made for a frosty start to the week and disrupted flights, roads and schools in Dunedin.

The temperature plummeted to 0C in Auckland overnight, with frosts possible in parts of the city.

In the south, some areas of Otago shivered through lows of -6C, while Dunedin and Queenstown got down to -3C overnight.

Icy conditions around Dunedin have prompted school closures, caused bus and flight disruptions and led to warnings for motorists on southern roads this morning.

The Northern Motorway out of Dunedin was closed for several hours this morning. It has since reopened but drivers are urged to take care.

Several Otago schools have closed for the day, while others delayed opening until 10am.

The New Zealand Transport Agency issued warnings for stretches of State Highway 1 from Glenavy in North Otago to Gore in Southland.

Cautions are also in place for SH88 from Dunedin to Port Chalmers, SH87 from Outram to Kyeburn, SH85 from Palmerston to Kyeburn, and SH90 from Raes Junction to McNab.

There was a likelihood of black ice on roads after snow to low levels on Saturday and Sunday. Eleven people were injured on Otago roads during the weekend after ice and snow created treacherous driving conditions.

Dunedin City Council said on its website there was widespread frost and black ice around the city, and advised motorists to avoid travel where possible.

Queenstown Lakes District Council also warned drivers to watch for severe frosts this morning. It said there was ice and grit on the Glenorchy Rd, SH6 from Frankton to Cromwell and SH6 from Wanaka to Haast Pass.

The NZTA advised motorists to carry chains if tackling the South Island's alpine passes.

Otago Regional Council said that owing to ice and snow, only some bus services were running in Dunedin. All southern routes were still planned to run, but this may change
There were delays at Dunedin and Queenstown airports this morning.

WeatherWatch head analyst Philip Duncan said the cold snap was meant to last for the start of the week - but today should be the coldest.

"We've had this big southerly blast, it's dredged up this very cold air which is now sitting over the country and we've got nationwide frosts this morning. The next couple of days are pretty cold and we'll see some frosts but this morning is probably the frostier morning.

"By Thursday, Friday we're back to northerlies ... it's going to be warmer by the end of the week, warmer and wet by Friday," he said.

He said it was a "very unusual" set-up in Auckland this morning with frosts in the city but cloud and showers offshore.

The cloud would roll in today, he said.

MetService said a northerly flow would bring rain to the north and west of both islands on Friday.

There was a low chance the rain could reach warning levels in Nelson, Buller, Westland, Taranaki, Northland, Coromandel and Bay of Plenty.

Snow is expected in the northern Hawkes Bay region and Gisborne early this morning, with a severe weather watch in place.

Auckland should expect a mainly fine day with a chance of showers and a high of 11C while Wellington is in for occasional showers and a high of 8C.

Today's forecast:

Whangarei:

Fine spells, few showers. High 12C, low 4C

Auckland:

Mainly fine, chance of shower. High 11C, low 4C

Hamilton:

Fine spells, morning frosts. High 11C, low -2C

Wellington:

Occasional showers, strong winds. High 8C, low 5C

Christchurch:

Cloudy periods with a few showers and possible sleet. High 7C, low 1C

Dunedin:

Morning showers, becoming fine. High 7C, low 0C

Queenstown:

Morning frosts, fine. High 7C, low -4C

Tomorrow's forecast:

Whangarei:

Fine, chance of showers. High 13C, low 6C

Auckland:

Fine. High 12C, low 6C

Hamilton:

Fine with morning frosts. High 12C, low 0C

Wellington:

Showers. High 9C, low 6C

Christchurch:

Morning showers, fine. High 8C, low -2C

Dunedin:

Fine with morning frosts. High 7C, low 2C

Queenstown:

Fine with frosts. High 8C, low -3C

(Source: MetService)

- Additional reporting from Otago Daily Times