Temperatures are forecast to turn icy this week across much of the country as a wintery blast sets in and coastal areas are being warned of large swells and "dangerous" conditions. 

Metservice is advising people to take a jacket and wrap up if heading outside, with frosty mornings and snow showers expected in some parts of the South Island. 

Temperatures at Aoraki/Mt Cook are set to dip to -4C overnight on Friday and Saturday and a road snowfall warning is in place for Crown Range Road and Milford Road from tomorrow evening. 

Metservice predicts Queenstown will plunge to -1C this weekend, 0C in Christchurch, 5 in Dunedin, and 7 in Wellington – but Auckland will stay relatively balmy with a low of 11C on Friday. 

 

Strong winds are forecast to set in tonight for most of the South Island and Wellington, persisting until tomorrow morning. 

A heavy rain warning starts tonight and early tomorrow morning for the Bay of Plenty, east of Opotiki, Westland and Fiordland, while a heavy rain watch is forecast for parts of Northland, Buller, Westland and the headwaters of Canterbury, Otago lakes and rivers. 

Meanwhile boaties near the Foveaux Strait are being warned of high swells, poor visibility and "very rough" seas between Thursday and Saturday, before easing on Sunday. 

"Large swell waves and dangerous coastal conditions are expected in the western marine areas of both the North and South Island from Thursday," Metservice said. 

"Combined waves are forecast to reach 6m for the western South Island later on Friday." 

 

Marine gale warnings have been issued around the Bay of Islands, Wellington and Cook Strait, and the Foveaux Strait. 

Metservice meteorologist Angus Hines said heavy falls, thunderstorms and hail are expected southwest of the country, and "maybe, just maybe, a small tornado near the coast". 

"We are expecting very heavy swell to develop as this week comes to a close," said Hines. 
 
"The western coastline first hit by large waves on Friday ... with 6-8m waves forecast for South Island coasts."