The rugby will be played under a roof but fans on their way to watch the All Blacks in Dunedin tonight have been warned of treacherous weather conditions.

And the weather around the rest of New Zealand won't be much cosier.

Rain, showers and thunderstorms have been forecast for most of the country this weekend.

The temperature in Auckland is unlikely to push past 15 degrees while further south, figures are expected to say in the negatives.

Super frost in #dunedin this morning! @WeatherWatchNZ #dunnerstunner pic.twitter.com/iF9hgKGAPz

— Sarah Gallagher (@SarahLibrarina) June 22, 2018

Police have this morning issued a release warning drivers in Dunedin to take extra precautions with ice on the roads in the city and hill suburbs.

Ice can be hard to see, and police are urging people to drive with extreme care as Dunedin's population swells with thousands of fans in town for the All Blacks v France test.

Conditions will be more favourable for tonight's third test against France, thanks to the roof on Forsyth Barr Stadium.

MetService's Dunedin forecast today is fine, with frosts and some cloud or fog in the morning, and northerlies developing later in the day. Temperatures will drop to about 6C by kick-off.

Parts of Otago and Southland may soon be hit by the heaviest snowfall so far this year, but it appears Dunedin and Oamaru will be spared.

MetService meteorologist Tui McInnes said a cold front from the Tasman Sea was expected to move northeast across the South Island tomorrow, bringing rainfall accumulations reaching warning amounts in Fiordland and Westland.

It was a chilly start to the day in Dunedin this morning. (Photo / Twitter)

"On Monday and Tuesday, there is moderate confidence of warning amounts of snow in Fiordland, Southland and parts of Otago above 300m.

"Fiordland, Southland, Central Otago, and Clutha are right in the firing line. It could bring up to 25cm of snow in 24 hours."

Given the nature of the weather event, he said the westerly wind was expected to shelter the coastal Otago region.

"It should keep places like Dunedin and Oamaru fairly clear [of snow]. At this stage, it is unlikely they will get any snow at low levels."

Otago and Southland residents were encouraged to keep up to date with possible changes to the forecast on the MetService website, and take care if driving.

Farmers were also encouraged to keep stock in sheltered areas.

McInnes said something else to look forward to was the days would now start to get longer.

"The longest night is over and the days are beginning to get longer again — only a few seconds at a time to start off.

"Unfortunately, it will stay cold for a while before it gets warmer again."

He said the inertia of the atmosphere meant there was a lag between temperatures warming and days lengthening again.

Additional reporting Otago Daily Times