Icy roads causing crashes, fog disrupting air travel on chilly day around NZ

Fog is again affecting travellers in Dunedin with at least one flight cancelled.

It is the second day in a row that fog has disrupted morning flights out of Dunedin Airport.

Air New Zealand flight 5756 was due to leave for Christchurch shortly after 6am on Wednesday but has been cancelled.

Dunedin Airport says travellers should check latest flight information with their airlines before arriving at the airport.

Meanwhile, a major highway in inland Canterbury has shut due to black ice and a multi-vehicle crash in icy conditions closed part of Dunedin Southern Motorway.

State Highway 8 between Lake Tekapo and Omarama is closed with motorists told to avoid the area or delay travel plans.

MetService meteorologist Devlin Lynden said the cold temperatures had been a result of clear skies overnight.

"We've seen frosty temperatures right around the country. And as far north as Auckland really, which is pretty rare for them," he said.

The Auckland suburb of Whenuapai dropped down to 1.3C on Wednesday morning while temperatures dropped to below 0 in several other regions, including Hutt Valley.

Parts of the central North Island plummeted to -5C and the Central Otago settlement of Lauder was greeted by a biting -6.3C.

Many other places from Canterbury to Southern Lakes, Central Otago, Dunedin and Southland were sitting between -3C and -5C, Lynden said.

Freezing conditions were set to continue for parts of the country over the next couple days.

"Tomorrow will be another cool one. This ridge of high pressure will stick around a wee while longer, possibly even a bit cooler than it has been this morning in a few places," Lynden said.

"But as we move closer to the weekend, these cooler temperatures are unlikely to stay around. A front moves in [consisting of] quite a warm, moist air mass moving in from the north.

"So I would expect temperatures to rise up and also as we head into the weekend, some rain for both the South and North Island through the weekend."

Icy roads causing crashes, closes highways

In a statement, Southern District Police said a number of crashes had occurred on Wednesday morning and motorists were being reminded to take care in icy conditions.

"There have been a number of crashes occurring within the district, especially in Roxburgh, Lumsden, the Dunedin Southern Motorway, and Cromwell.

"Please remember to slow down, drive to the conditions, keep your distance, and drive rested and unimpaired."

As well as the closure of State Highway 8 between Lake Tekapo and Omarama, State Highway 1/Dunedin Southern Motorway was closed from the Riselaw Road overbridge to southbound traffic after a crash in icy conditions.

Emergency services were called to State Highway 1 near the Main South Road off-ramp about 7.30am following the four-vehicle crash.

One person received moderate injuries and another received minor injuries.

In a statement, NZTA said: "As forecast, freezing temperatures are affecting roads throughout the central South Island this morning, and caution is being urged on all inland highways.

"Roading crews have been laying grit on roads to improve traction in the freezing conditions, but roads will only be reopened when considered safe."

A thick freezing fog had also caused damp roads and ice around the Queenstown-Lakes district.

The council said negative temperatures across the district was causing difficult conditions.

"Cardrona Valley and Crown Range Road are cold and frosty with icy conditions. Grit has been applied.

"[On Tuesday] the road crews were working non-stop from 5am until 3.30pm and they'll likely do the same today."

The frosty starts come after the National Institute of Water and Atmospheric Research reported that June was an extremely warm month across all of New Zealand.

Dozens of locations had their warmest or near warmest June on record.

Places like Christchurch, Nelson, and the Bay of Plenty were warmer than average.

Many areas were at least two degrees hotter than they'd usually be this time of year.