Snow is causing havoc on the South Island's roads as wild weather continues to batter the country.

WeatherWatch said the storm was now peaking over the country but some places should brace for another rough 48 hours.

"Monday, Tuesday and Wednesday are probably the peak days of this storm with heavy snow in the south, gales in the east and north and hail, thunder and squalls in the west and north west," said WeatherWatch head analyst Philip Duncan.

In Queenstown police have been dealing with dozens of single-car crashes as drivers ignore the obviously hazardous road conditions.

A 10-tonne truck nearly drove through the front of the Queenstown District Court this morning after it skidded across an icy road.

Queenstown police Acting Sergeant Blair Duffy said the fully-laden truck had stopped at the top of a steep hill on Stanley St because the driver thought it looked too dangerous to go down, but when he saw another truck successfully navigate the drop he thought he would "chance his arm".

"He couldn't control it and it hit the kerb and came to a stop literally right outside the two sliding doors of the court. It was sitting pretty precariously, leaning in towards the court house."

Also on Stanley St, the slushy snow caused five cars to lose control on the same corner and end up mounted in a line against the footpath.

No one was injured in today's crashes, but with the weather expected to get even colder later this week, ice on the roads would make driving even more dangerous, Mr Duffy said.

"It's just a given that you should be using chains in this weather. It's just a given. As soon as you leave home and see what these road conditions are there's no excuse for not putting chains on.

"I know it's unpleasant but it could at the end of the day save your car getting damaged and potentially save a life."

The snow also caused five trucks to get stuck on the main highway out of Alexandra this morning.

At least one school in Queenstown, Wakatipu High School, was closed today because of the snow.

In Northland, a woman escaped unhurt when a tornado ripped part of the roof of her house early today.

The twister caused a 75-metre swathe of destruction through Kaiwaka, 62km south of Whangarei about 1am, tearing off half the woman's roof, leaving the other half intact.

Firemen headed to the house were greeted by insulation products and other debris flung about by the wind, Kaiwaka chief fire officer John Bowman said.

"I have never seen it (damage) quite as bad in a house."

Metservice issued severe weather warnings for Wairarapa, Hawke's Bay, Gisborne, Westland, Fiordland, Marlborough, Nelson, Canterbury, Wellington, Southland.

A heavy snow warning remains in force for southern Westland and Fiordland.

There were reports of light snow fall in central Dunedin and on surrounding hills.

Winds of about 100km/h were expected from Taranaki to Taihape and southward to the Kapiti Coast this evening.

The inclement weather has been welcomed by some. North Island skiers will be delighted to hear that more than 1m of snow has fallen on Mt Ruapehu, soaring past July 2010 levels.

"Best of all, the weather is predicted to clear later in the week and we expect a beautiful start to the school holidays," said the Ruapehu skifield's general manager, Dave Mazey.

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