Canterbury Weather Update said snow covered parts of North Canterbury overnight and into Tuesday morning.
Sleet and snow showers were reported in Rangiora and Pegasus, north of Christchurch.
MetService issued road snow warnings for Arthur’s Pass, Lewis Pass and Porters Pass, with flurries potentially reaching down to 200m in the Canterbury Plains.
MetService said Banks Peninsula could also see snow fall to about 200-300m.
Conditions in Christchurch started to clear at 8am but the snow was expected to linger in some parts of Canterbury until this evening.
MetService meteorologist John Law told RNZ there has been a dusting of snow at Mount Cook and some of the higher passes and showers in Southland and Otago.
All southern highways are now open, though motorists are warned to expect winter conditions and have been urged to take care.
The Milford Road (SH94), Lindis Pass (SH8) and SH93 Mataura to Clinton were all closed earlier this morning but had reopened by 10am. SH8 remained closed as of 10.30am at Burkes Pass in Canterbury.
The Milford Road is due to close again at 5pm. Danseys Pass Rd is also closed. Road gritting is being carried out across the South Island.
Meanwhile, Southland District Council says the following schools are closed: Te Tipua Primary School, Lumsden Primary School, Northern Southland College, Mossburn Primary School, Balfour Primary School.