Foul weather heads north after rain soaks south

Snow could reach as far north as Coromandel and the Kaimai Ranges later this week as a huge winter storm looks set to batter the country.

The polar blast prediction comes after heavy rain caused havoc in the South Island yesterday.

Roads flooded and schools were closed in Christchurch, and Dunedin was cut off from the north by flooding as Otago rivers ran at record highs.

Forecasters said the huge slow-moving low which brought the heavy rain would continue to bring unsettled weather.

WeatherWatch head analyst Philip Duncan said a polar blast would bring heavy snow to the southern and eastern coastlines of both islands later this week, with snow to sea level in the South Island and near to sea level in parts of the North Island.

"Nowhere in New Zealand can escape it. This is such a huge system."

The storm would hit the South Island tomorrow before spreading north over the entire country on Thursday and Friday. It would ease on Saturday before more rain and wind on Sunday.

Mr Duncan said Auckland could expect a "very cold" change with a high risk of hail, the chance of thunder and possible snow flurries in the ranges. He said the storm was almost identical to one in winter 2011 which saw snow falling but not settling in Auckland.

But although snow was likely in the Coromandel and Kaimai ranges, it was unclear whether it would get as far as Bombay or Hunua.

MetService media and communications meteorologist Daniel Corbett said the largest snowfalls were likely in inland Canterbury and Marlborough, and near sea level from Southland to Kaikoura by Thursday.

He said it was a "very dynamic weather situation" and details about where and how much snow was expected could change.

Authorities in the South Island were last night bracing for more flooding as the regions continued to be hammered by rain.

In Christchurch, a welfare centre was set up to help people affected by city-wide flooding. Persistent rain caused traffic chaos in the city and forced the closure of roads and bridges. Some schools were also forced to close for the day.

In Otago, dozens of roads were flooded and State Highway One between Dunedin and Oamaru was closed at several points.

Civil Defence authorities were keeping an eye on homes in Waitaki, with rivers running at record highs.

In the Tasman district, where the heavy rain caused a fatal landslip on Sunday, a number of roads were closed due to flooding or slips.