People still grappling with flooding in the South Island are now being warned of the snow storm about to hit much of the country.
Bitterly cold Antarctic air is expected to bring snow showers which could fall to low levels as far north as central New Zealand.
The heavy rain has already closed the rail link south of Chistchurch. Traffic diversions are also in place around Oamaru because of the damaged bridge near Timaru.
There are also problems for motorists on the main road out of the North Canterbury town of Rangiora with the Ashley River Bridge closing in.
One of the bridge's piers has been swept away by high flood waters and it is too soon to know how long the bridge may be closed, says Waimakariri District Council's Utilities and Roading Manager, Gerard Cleary.
The bridge suffered similar damage in 2010. But how long the bridge will be out of service cannot be confirmed until the river level drops and a detailed inspection is undertaken.
Largest snowfalls at this stage seem likely about inland Canterbury and Marlborough, while snow may fall to near sea level from Southland to Kaikoura by Thursday, MetService said.
"This winter storm will have quite a bit of bark and bite, and is expected to bring widespread severe weather for much of New Zealand," MetService's Daniel Corbett said.
Civil Defence is urging Canterbury residents to stock up on food, water and warm clothing ahead of the predicted cold snap.
ONE News reporter Joy Reid tweeted that supermarkets have been busy in Christchurch as people stock up ahead of forecast snow and supermarket shelves have been stripped bare.
In previous years heavy snowfall has led to road closures and power outages affecting large parts of Canterbury.
A heavy snow fall in June last year cut power to thousands of homes, left many roads impassable and disrupted flight services.
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Canterbury Civil Defence said the snow forecast for this week could be as bad, or worse, than last year.
"Everyone should have the necessities in place to be able to be self-sufficient for three days or more in the event of road closures and power cuts," said Neville Reilly, Regional Civil Defence Group Controller.
"This includes having stocks of food, water, warm clothing, fuel, alternative lighting and other emergency supplies on hand."
Christchurch Police say the biggest factor in the winter road toll is motorists failing to drive to the conditions. They are urging motorists to drive to the conditions and be wary of ice hazards which may follow in the wake of snow.
Last year 10 people died on Canterbury roads between May and August.
Very strong westerlies from Northland to Taranaki may result in high wind gusts on Thursday. MetService said large waves are also expected on many beaches.
"This very intense and significant winter storm will slowly ease by the weekend, leaving cold frosty nights in its wake," Mr Corbett said.
Otago river levels
Despite heavy rain easing in the region this morning, many Otago rivers are continuing to run at high levels.
The Otago Regional Council advises that the Taieri River level is now beginning to fall but is expected to remain at flood alert levels for at least 24 hours.
The spillway gates and flood banks of the Lower Taieri Flood Protection Scheme functioned as expected, the council reports.
While the Pomahaka River, the North Otago catchment rivers and the flows of water in the Leith and Lindsay Creeks are beginning to return to normal levels.
However, the Lower Clutha river is continuing to rise and will remain high as water from upper catchments drain into it. Motorists are advised that minor surface flooding is expected in low-lying areas near the river.