Fog disrupts air travel from Dunedin 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.

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

It's been a chilly start to the day for many around the country, with Hamilton and Blenheim sitting on -1 degree Celsius this morning, while Timaru and Queenstown started on -3 and Christchurch -2.

MetService is forecasting frosty mornings as far north as Thames this week, and everyone can expect to plunge to single digits overnight.

Auckland is forecast to have maximum temperatures in the mid-teens this week and Christchurch will be only just making it into the double digits until Thursday, MetService says.

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.

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."