A strong cold southerly airflow over the South Island spreads over the North Island today, bringing rain and a risk of heavy showers, hail and snow to low levels.
Snow is forecast down to 200m for the eastern and southern South Island and a heavy snow watch is out for Canterbury, including Banks Peninsula, Fiordland, Southland and Otago.
Snow was expected to start falling last night and is forecast to continue until this afternoon.
Heavy snow and hail have already fallen in Dunedin hill suburbs and across parts of the region last night.
The Dunedin City Council has advised road users to take care and drive to the conditions. Three Mile Hill and Mount Cargill are closed and black ice is likely lower down.
A number of schools around Dunedin's hill suburbs are starting at 10am because of the snow and some bus services have been affected.
Brockville School, Waikari School, Halfway Bush School, St Mary's School Kaikorai, Pine Hill School, East Taieri School, Columba College, Bradford School and Rudolf Steiner Kindy and School will all start later today.
The Central Otago District Council advised people to check if schools were open before travelling.
Wakatipu High School, Queenstown Primary and Shotover Primary are closed for today.
All other schools in the Wakatipu Basin will not open until 10.30am.
Hurunui District Council had also received reports of snow showers in Greta Valley, Rangiora, Cheviot and parts of North Canterbury, where snow is settling to about 150m and heavy falls around 400m.
Clutha District Council said about 12-15cm of snow fell on Mt Stuart and 10-12cm in Tapanui/Heriot overnight.
A logging contractor told the council about 10cm of snow had fallen on Wilden School Rd.
Rain first thing this morning has resulted in a lot of black ice around the district so road users need to take care especially as the sun comes up, it said.
Road snowfall warnings are also in place for Lewis Pass, Arthurs Pass, Porters Pass, Lindis Pass, Crown Range and Milford Rds and SH1 from Dunedin to Waitati.
The Crown Range was closed overnight because of snow, along with SH94 from Te Anau to Milford Sound, which was expected to open about 10am.
SH93 from Mataura to Clinton is also closed until further notice, as is the Lindis Pass from Cromwell to Omarama and SH8 from Alexandra to Roxburgh.
Chains are also essential on SH73 from Springfield to Arthurs Pass, SH73 from Arthurs Pass to Otira, SH85 from Alexandra to Kyeburn, SH85 from Kyeburn to Palmerston, SH6 from Wanaka to Cromwell.
Warnings are also in place for SH8 from Twizel to Fairlie, SH6 from Ross to Haast, SH8 from Alexandra to Raes Junction, SH8 from Milton to Raes Junction, SH90 from Raes Junction to McNab, SH87 from Outram to Kyeburn, SH96 from Winton to Mataura, SH94 from Lumsden to Gore, SH94 from Te Anau to Mossburn and SH1from Palmerston to Gore.
Along with road disruptions, Air New Zealand is reporting that adverse weather conditions across the South Island may cause disruptions to their services today and advises customers to check their website before travelling.
There is a low risk of thunderstorms over the South Island, about the east coast from Clutha to Marlborough, and also about coastal parts of northern Westland, Buller and western Nelson.
MetService meteorologist Sarah Sparks said snow is already reportedly falling to 200m in Southland, which is a good indicator much of Otago, Dunedin, Fiordland and Clutha will be getting snow.
"Looking at the Queenstown webcam they are covered in snow, and they are at 370m so that makes sense because that is well above the 200m level we were forecasting."
Sparks said the cold front was moving onto the North Island this morning, and is now bringing showers to the upper South Island and lower North Island.
"We can see some chunkier, heavier showers around Buller and Marlborough at the moment, and it is starting to move north to Taranaki, Wellington, Manawatū and Whanganui.
"That will then move further on to coastal Waikato, Auckland and Northland, as well as up the east coast of the North Island – Wairarapa, Hawke's Bay and Gisborne."
The North Island will also get snow to 500m over the Tararua Range and 600m further north affecting the Desert Rd and the Napier-Taupō Rd and warnings are in place.
A snow warning has also been issued for the Rimutaka Hill Rd.
There is also a moderate risk of a few thunderstorms about Whanganui and Taranaki late morning, and a low risk about other coastal areas from Waitomo to Wellington and Wairarapa.
Strong southerlies will also effect exposed areas this morning and Wellington can expect gusts up to 90km/h in exposed places. However, these are forecast to ease during the day as the low moves east.
Sparks said while the current low will move away later today, another feature is expected to hit the South Island tonight, from the south west.
"It is not quite the same as the last one, it was quite an active cold front whereas this is slightly warmer – but we are still expecting some snow with that as well but not to quite as low levels."
From late Thursday, a ridge of high pressure spreads onto New Zealand from the Tasman Sea bringing more settled conditions.
• Whangarei: Cloudy. Showers developing from late morning. Southwesterlies strengthening late morning. High 15C / Low 6C.
• Auckland: Showers developing morning, possibly heavy and thundery from evening. Fresh southwesterlies. High 14C / Low 6C.
• Tauranga: Long fine spells. A few showers, mainly afternoon. Westerlies turn southerly early evening. High 14C / Low 3C.
• Hamilton: Cloudy periods. Showers developing morning, clearing evening. Westerlies turn southerly late afternoon. High 12C / Low 1C.
• New Plymouth: Showers, possibly heavy and thundery in the morning, clearing evening. Westerlies turning southerly afternoon. High 13C / Low 3C.
• Napier: Cloudy periods. Rain from late morning then gradually easing. Southwesterly strengthening afternoon. High 12C / Low 3C.
• Palmerston North: Showers clearing by evening. Southerly developing morning. High 11C / Low 1C.
• Wellington: Rain developing morning, then showers, some heavy with hail, easing by evening. Gale southerly. High 10C / Low 5C.
• Nelson: Morning cloud and chance shower, then fine. Gusty southerlies. High 11C / Low 1C.
• Christchurch: Rain, possibly heavy with hail, easing to a few showers by afternoon. Chance snow morning. Strong southerlies easing evening. High 7C / Low 3C.
• Greymouth: Mostly sunny with morning frosts. Gusty southerlies easing. High 10C / Low 2C.
• Dunedin: Showers, possibly heavy with hail before dawn, and snow to 200 metres in the morning. Strong southwest. High 8C / Low 5C.
• Queenstown: Snow showers, becoming few and far between in the morning. Sleety rain developing at night. Gusty southerly. High 6C / Low 0C.
• Invercargill: Showers, some possibly heavy with hail before dawn. A period of evening rain. Strong southwesterlies. High 10C / Low 6C.