Southwesterlies will bring temperature drop, heavy showers and squalls

A late cold snap has brought fresh snow to Mt Ruapehu's ski slopes just in time for the school holidays.

Snow has fallen to 1100 metres, with an average of 15-20cm on the upper slopes and 30cm in the gullies. More snow is forecast today.

Whakapapa Ski Area manager Steve McGill said patrol teams had reported snow pockets up to 40cm deep in places, and described the fresh snow as Mt Ruapehu Champagne Powder - low-density, soft snow.

"The snowfall couldn't have come at a better time. It's a great bonus for this time of year, topping up the trails as we head into the spring season. It's also great timing for the school holidays," Mr McGill said.

Advertisement says that while some places will bask in high temperatures during the week, most will feel a cold bite this weekend.

Head analyst Philip Duncan said the weather would turn southwesterly, bringing heavy showers, squalls and a noticeable drop in temperatures.

The air temperature should gradually rise as the week wears on. Christchurch is expected to reach into the low 20s on Friday - then drop to only 12C on Saturday.

But it was the deep south that would be most exposed to the post-winter surge, Mr Duncan said.

"We have a high over Tasmania and a low southeast of New Zealand. It's the perfect set-up to drive in wintry southerlies."

Parts of Southland and Otago were likely to see hail and sleet on Saturday, Mr Duncan said.

Meanwhile, Niwa released its climate summary for September, which reported a wet month for western regions of the South Island, as well as for Nelson, Southland and Central Otago.

In contrast, eastern areas of both islands experienced a dry September.

It was a sunny month for eastern parts of both islands, cloudy for Westland and there was close to average sunshine everywhere else, the Niwa summary said.