And on Boxing Day revellers may want to head to the sales instead of the beach, as a front moving up the country is forecast to bring rain.
MetService meteorologist Tom Adams said temperatures would drop markedly in the South Island with the front.
"Christchurch which is 31C on Christmas Day is only expected to reach 18C on Boxing Day," he said.
"The whole country overall [will be] feeling quite a lot chillier on Boxing Day night, down in the single figures for quite a lot of the South Island."
In Queenstown it could be as cold as 6C and Ashburton and Timaru may get an overnight low of 8C.
But behind the cold front is a high that should spread over the country from Tuesday.
"It's looking quite nice with high pressure over the country as we head towards the end of 2017," Adams told the Weekend Herald.
However, the forecast for New Year's Eve was a bit uncertain.
"By the time we get to the 30th we start to see another feature approaching from the west - it's almost spring like the weather pattern we're in - high pressure sitting predominantly over the North Island and fronts coming in quite rapidly west to east," Adams said.
"It's quite likely that [another] front would cross over New Year's Eve in a similar kind of pattern to what we're seeing over Christmas - a low pressure system forms to the east of the country and there's some variations in models about how close it stays to New Zealand."
If the low did hang around it would be unwelcome to Rhythm & Vines festival-goers as Adams said it could bring rain to Gisborne and the Hawke's Bay until December 30.
Parts of the South Island could also get rain on New Year's Eve - but those attending Rhythm & Alps in Cardrona Valley will be thankful that any wet weather is likely to bypass them.
"Places like Wanaka are pretty sheltered from this kind of set-up. It would take a more serious type of front to bring rain into Wanaka," Adams said.
Today's forecast
Whangarei: Mostly cloudy, with one or two showers, high of 24C
Auckland: Morning cloud and chance early shower, then fine. Northeast winds, 25C high
Hamilton: Mostly cloudy, chance shower. Light winds, 24C high
Tauranga: Partly cloudy, chance shower. Light winds and sea breezes, 24C high
Napier: Fine spells. Light winds and sea breezes, 22C high
Wellington: Fine and warm. Light winds, high of 25C
Nelson: Fine, apart from some morning cloud. Light winds and sea breezes, 23C high
Christchurch: Cloudy morning and night, otherwise fine. Northeasterlies picking up in the afternoon, high of 22C
Dunedin: Mainly fine, but some cloud morning and night. Chance afternoon shower. Northeasterlies, high of 22C
(Source: MetService)
