Wretched weekend of weather

More snow is forecast for much of the country this weekend. Photo / Otago Daily Times

A harsh winter weekend which is expected to bring snow to sea level has kicked off with reports of a tornado ripping through a Northland property.

A wintery blast set to hit New Zealand may bring an "incredibly rare" mix of snow and sleet to North Island centres including Wellington, a forecaster predicts.

The weekend has started with the tornado that hit land between Waipu and Waipu Cove at about 4.30pm this afternoon.

It flattened a shed and caravans, while trees were uprooted by the force of the winds.

There has also been a sewage spill in Whangarei caused by heavy rain and several roads in the area have been flooded.

The District Council advised people to avoid flooded areas and report any popped-out man holes.

Weather Watch's lightning tracker had picked up more than 175 lighting strikes in Northland and north of New Zealand this afternoon.

A cold July weekend

Metservice this afternoon said a low pressure system that brought rain and snow to the North Island this week would soon give way to wintery conditions "straight from the Antarctic".

It said the weather conditions should see snow fall to low levels in much of the South Island and parts of the North Island.

Weatherwatch.co.nz head forecaster Philip Duncan said his data showed North Island centres including Palmerston North, Taupo and hilltop suburbs in Wellington would be on the "borderline" of snow fall.

"It's unlikely to settle but shows just how cold this southerly change will be."

Waiouru, Ohakune and Taihape were expected to be blanketed with snow.

Metservice meteorologist Daniel Corbett said snow was expected to reach sea level in Southland and Otago on Sunday morning, he said.

The wintery blast was then expected to sweep northward on Sunday afternoon and Monday, bringing snow to near sea level in Canterbury and Malborough.

"This storm also has the potential to bring settling snow to many parts of the South Island."

Mr Corbett said the cold weather would spread to the North Island late on Sunday, with snow blanketing on the Desert Rd and much of Taihape on Monday.

The Rimutaka Hill Road and the Napier-Taupo Road could be at risk from snowfalls from early Monday, while Wellington residents could even see snow on hills surrounding the city, he said.

Meanwhile, heavy rain is set to strike Gisborne and Hawkes Bay this afternoon.

Up to 120mm rain could fall on Hawkes Bay ranges, Metservice warned.

Rivers and streams could rise rapidly, and slips and surface flooding was possible in those areas, it said.

WeatherWatch.co.nz said a band of rain is moving down Northland and will reach Auckland early this evening.

There was a low risk of isolated thunder or lightning tonight in Auckland and a moderate risk for Northland, it said.

Dodgy roads

Two trucks were blown over by the wintery blast this morning, Constable Amy Ryan of Palmerston North police said.

One was near Otaki in the Horowhenua, and the other on State Highway 56 between Shannon and Palmerston North, she told NZPA.

No one was injured and the roads had been cleared, but police are still urging caution on New Zealand roads as the severe weather approaches.

In Canterbury, police are warning motorists to exercise extreme caution.

Acting Road Policing Manager Senior Sergeant Glenn Nalder says drivers should brace for difficult road conditions, with snow predicted to fall to near sea level across the region from Saturday.

"Unfortunately the severe weather forecast falls in the middle of the school holidays, when a significant number of vehicles will be on the roads.

"The last thing we want is for family holidays to be devastated by crashes. I'd urge drivers to plan their travel carefully and consider delaying journeys until weather conditions improve - a short delay is a small price to pay for a safer journey.

"As well as low level snow there will be risks of frost and ice on the roads, especially in rural areas. Motorists should slow down and watch out for potential hazards."

- HERALD ONLINE, NZPA