Weather forecast: Black ice and frost keep nippy grasp on NZ

Black ice and frost has hit the South Island causing crashes and police warning drivers to be careful.

Two vehicles flipped after hitting black ice in the South Island this morning.

The crashes, on Malaghans Rd in Queenstown, did not result in any serious injuries.

Police have urged southern motorists to take extra care on the roads as light rain on the roads has turned to black ice in the Otago Lakes area, and elsewhere.

The risk of snow has passed on Lindis Pass, and the warning has been lifted.

The coldest spot last night was Tongariro National Park which got down to -5°C. Hamilton had freezing fog throughout the night and early morning when it plunged to -2°C. Christchurch had a massive variation in temperatures with it reaching -1°C at the airport and 10°C on the coast.

Today will see mostly fine weather for inland areas with cloud covering the South Island and showers nibbling at the edges around Gisborne, Greymouth and Nelson.

Tonight the North Island will see frostier temperatures and MetService forecaster Tuporo Marsters advised areas around the high central plateau were likely to get black ice.

Heavy rain and strong winds are expected as the second large low in a week approaches this weekend. Wet weather is forecast for the northwest and west coast of the South Island plus the western side and upper half of the North Island.

WeatherWatch warned that rain may turn to heavy snow above 400m in Southland and Otago on Sunday.

Strong winds are forecast to rip through central New Zealand from the Wairarapa through to Marlborough.

Colder in the north this morning. Cloud cover kept the South Island slightly warmer. Find out why https://t.co/aKlFbSUdAC ^JR pic.twitter.com/NUM3xje4Kz

— MetService (@MetService) June 26, 2017

Yesterday Kiwis woke up to severe frosts and temperatures deep in the negatives.

Mt Cook Airport and Pukaki Airport were the chilliest at -6C. Christchurch was frosty at -3C, Dunedin 1C, Wellington 7C, Auckland 10C and Whangarei 8C.

The Queenstown Lakes District Council said conditions we're "extreme" on roads in the area, and urged motorists to take extra care. Danseys Pass Rd was closed because of snow.

MetService meteorologist April Clark said there were three factors which contributed towards a cold night.

The first is the swing from warm tropical air from the north to cold southerly air from the South Pole. The second is whether a thick blanket of cloud is present to keep the warmth in and the final factor is how high above sea level you are. Clark said the temperature would decrease between 6°C and 10°C for every kilometre you rise.

"This means, all things being equal, Taupo, sitting 400 metres above mean sea level will be about 4 degrees colder than a coastal city such as Napier on a dry day."