Weather experts predict southerly polar blast

Winter looks set to arrive on schedule as weather experts predict a southerly polar blast to ice the country early next week.

Forecasters say this weekend will be wet in the north, and mild and dry in the South Island as a westerly flow brings a touch of late Autumn warmth.

But before an expected dry Queen's Birthday weekend, temperatures will plummet early next week and will stay in single digits for up to three days.

The snowy, southerly blast could bring snow down to near sea level for Southland, much of Otago and exposed areas of Canterbury.

And both Dunedin and Christchurch have the chance of fleeting snowy showers, according to WeatherWatch analyst Richard Green.

"The air temperatures look very cold for places such as Canterbury southwards but it's the amount of rain or snow and the wind direction that will be the difference between a few rain showers or snow showers for Cantabs," Mr Green said.

"It's early for this sort of event but not unheard of and frosts following this system could be fairly severe in places for a night or two."

Invercargill and Gore have a reasonable risk of snow flurries and also thundery showers, he said, but Queenstown and Alexandra are looking at a 70 per cent chance of snowy conditions.

WeatherWatch believes the North Island won't escape the cold either with snow possibly dropping as low as 300-500 metres for a time over hilly areas across the east and south.

Alpine passes in the South Island, the Tararuas and Central Plateau, including the Desert Road, could be vulnerable to the snow and ice.

Queen's Birthday weekend still holds the promise of mainly dry skies for much of the country.

But Mr Green warned that the west and south of the South Island could see rain sweep across later in the long weekend with a nor' wester picking up.