Temperatures plummet as icy blast sweeps country

New Zealanders are having a freezing start to the weekend as the coldest forecast winter in years begins to set in.

MetService is predicting temperatures to hit single-figures across the country on Saturday, leaving some South Island roads treacherous with black ice.

Already this week the country has been thrashed by snowfall and wind down south, and thousands of lightning strikes accompanied by heavy rain and thunder in the North Island.

On Friday, MetService warned Newshub that in terms of temperatures, the worst was still to come.

"There is a southerly change coming through over lower South Island [on Friday night] so it's certainly going to feel cold," forecaster Stephen Glassey said.

"That southerly makes its way up the islands... [Saturday] will be colder than it is [on Friday]."

Strong winds are expected along the southern and eastern coasts, and a potential for severe gale southerlies in coastal areas from Banks Peninsula to Gisborne from Sunday.

There is also a low chance of heavy snow above 400m in Canterbury and the Kaikoura Ranges.

Roger Venn from the AA says avoid driving in wintry conditions if you can.

"If you do have to drive, put your lights on," Mr Venn told Newshub.

"Make sure your windows and mirrors are all nice and clean, and defrosted. Just take your time - slow down.

"Just because we're not used to driving in those conditions very often, it becomes a bit of a surprise to us. More people are driving I guess because they want to keep out of the rain."

On Wednesday the wintry blast should ease off as a ridge of high pressure builds over the South Island.

Newshub.