NZ Transport Agency Waka Kotahi advised of the first closures - on State Highway 8 from Twizel to Fairlie and SH80 from Pukaki to Mt Cook - about 6.15pm.
The closures, owing to forecast ice and snow, start from 8pm today and are scheduled through to 8am tomorrow, though their reopening is weather-dependent, NZTA says.
In an update at 7.15pm NZTA said SH73 (Porters Pass) was closed just before 7pm because of ice and snow, while on the West Coast, SH6 was closed between Ross and Hari Hari after strong winds brought trees down.
The news comes after snow fell on the Crown Range and in parts of Otago today, prompting warnings for motorists to be "sensible" and prepared for widespread disruptions.
Weather warnings were in place for much of the South today but by this evening most had been lifted.
The Lindis Pass, between Omarama and Tarras on SH8 is catching snow but remains open, with electronic signs warning drivers of the need to take care and slow down, NZTA said.
The heaviest snow has now shifted northwards, with warnings in place for Canterbury from about noon on Monday for the north and south Canterbury high country regions, and the foothills about and south of the Rangitata River.
MetService has extended several snowfall warnings for a number of South Island highways, RNZ reported.
Up to 60cm of snow was expected to settle on SH73 at Porters Pass through until 9pm tomorrow, with more to fall higher up.
In Arthur's Pass (SH73), up to 10cm of snow was expected to settle near the summit, through until 6pm tomorrow.
In Lewis Pass (SH7), between 8cm and 15cm of snow was expected to fall on the road before 11pm tomorrow.
The Mt Cook/Aoraki highway (SH80) from the base of Lake Pukaki/the SH8 intersection to Mt Cook Village was closed this morning but had reopened by early afternoon.
SH8 from Fairlie through Burkes Pass to Tekapo reopened before midday, and Tekapo to Pukaki was open again after 11am.
NZ Transport Agency Waka Kotahi system manager Mark Pinner advised motorists to check the NZTA traffic and travel pages for updates, such as whether chains are required.
"In South Canterbury we have seven crews busy gritting and clearing snow today,” Pinner said.
"We have additional resources on standby around the central and lower South Island as the forecast is for snow to continue to around 2am tomorrow/Wednesday morning.
"The alpine passes between Canterbury and the West Coast could catch snow from midday today into Wednesday."
CHAINS NEEDED FOR CROWN RANGE
Snow blanketed the summit of the Crown Range, linking Queenstown and Wānaka, this morning and chains must be fitted if driving this alpine road.
A Queenstown Lakes District Council spokeswoman said more snow was expected throughout the day and road users were asked to follow crew instructions at checkpoints.
Elsewhere, the roads are wet and temperatures were reasonably warm and sitting above zero about 7am.
"This will likely change and there's a good chance the roads will get icy later in the morning. Expect a few rocks on the road if heading through the Kawarau Gorge."
In Central Otago, wet roads were being reported across the district with some strong wind gusts. A spokeswoman for the district council said there had been sleet and snow flurries in Manuherekia and Maniototo areas but it was not settling yet.
Dansey’s Pass Road is closed (from the gates past the Dansey’s Pass Hotel), due to snow and ice on the Waitaki side.
The Milford Road (SH94) in Southland remained open.
- additional reporting ODT Online and Star News
