The MetService also lifted heavy snowfall warnings with only light showers expected near Ohakune and Raetihi.
The Desert Road had been closed as conditions were too treacherous for motorists -- a truck and trailer having jack-knifed this morning, blocking both lanes north of Waiouru. Seven trucks which became stranded on SH4, north of Ohakune, from around 3am, unable to negotiate the incline through the National Park as snow and ice coated the roads.
Roading crews worked this morning to free them as the road warmed enough to clear a path.
Black ice in Taranaki meant a number of vehicles slid off the road, although no injuries were reported.
Police patrol cars were out leading traffic as most crashes were caused by people going too fast for conditions, Stratford police acting Sergeant Dave Lindsay said.
"But even in the patrol car we were getting some people trying to overtake us. Obviously they were in a hurry to get to work." Police attended at least six accidents between Stratford and New Plymouth this morning.
Rotorua awoke to the rare sight of snow this morning with the eastern suburbs and hills behind the airport coated.
Weather analyst Philip Duncan said the cold snap was set to continue until tomorrow as winter had "well and truly arrived early".
"It's like we haven't had an autumn. "We are two months away from the coldest part of the year, so to see temperatures this low is certainly eyebrow-raising." Southerlies were expected to continue chilling the North Island until at least tomorrow, possibly through to Sunday, he said.
All roads were open in the South Island but motorists were urged to drive with care.
