The majority of the North Island is in for relatively fine weather on Christmas Day, while some in the south with their hearts set on the classic Kiwi barbecue may need a back-up plan - as they may be in for a White Christmas instead.

Forecaster MetService said Christmas Day in Auckland will be slightly cooler and less humid than the scorching temperatures the city has seen recently.

A fine day with high clouds is on the cards for Auckland with the southwesterly winds set to make the big day feel cooler.

MetService meteorologist Lewis Ferris said the same settled weather is forecast across the majority of the North Island on December 25.

Rain was initially forecast for Wellington on Friday - but it's now looking drier with cloudy periods, light winds, and northerlies developing in the evening, with a high of 19C, Ferris said.

"At times, we should see the sun, mixed in with the cloud," Ferris said.

But the story isn't so good for Christmas Day in the South, he said.

"Places like Nelson and Marlborough should be in for an all right Christmas day, but stretching down the east coast from Christchurch down to Dunedin looks like they will see some wet weather through the day and some cooler temperatures as well."

MetService meteorologist Peter Little said those in the south planning on a Christmas meal outdoors may need a back-up plan.

"Although the forecast is dry for much of the country on Christmas Day, there will be some places that get rain or showers, especially in the south."

"Snow is forecast down to 1000m over the South Island this weekend, and a maximum temperature of just 13C is forecast for Ashburton on Saturday, which is around 8C below average for this time of year."

Niwa has touted the possibility of a "White Christmas" in the high peaks of the South Island – where temperatures are set to dip below zero.

MetService meteorologist Mmathapelo Makgabutlane said the snow will mostly fall on Boxing Day.

"We are expecting snow mostly for the lower South island ranges going down to about 1000m in the Canterbury high country and southern Fiordland."

The weather is due to a low pressure system moving across the country from the east, the south-westerly flow brings cold air with it, Makgabutlane said.

Wellington is set to creep down to 14C - which is about six degrees below average, while Masterton is forecast to hit 15C, about 8C below average.

Christmas Day forecasts

Whangārei Fine with high cloud. Southwesterlies. 24C high. 14C low.

Auckland Fine spells with high cloud. Southwesterlies easing. 21C, 15C.

Hamilton Fine spells with increasing high cloud and southwesterlies 22C, 9C.

Tauranga Fine, with increasing high cloud. Southwesterlies. 25C, 13C.

New Plymouth Fine spells and southwesterlies. 20C, 12C.

Rotorua Fine spells with increasing high cloud. 23C, 10C.

Napier Fine, southerlies with increasing high cloud. 25C, 14C.

Wellington ​ Cloudy periods. Light winds, northerlies developing evening. 19C, 12C.

Nelson ​Fine with light winds. 22C, 11C.

Christchurch​ Mostly cloudy. A few showers, mainly from afternoon. Southerlies, turning northeast in the afternoon. 16C, 8C.

Dunedin ​ Cloudy periods. A few showers from afternoon as southwesterlies turn northeast. 16C, 8C.