"It's expected to get to 21C - the same as Christmas Day - but there'll be a little less wind so it could feel warmer."
There was a similar pattern around the rest of the country, with the odd shower or morning cloud clearing as the day progressed. Most places would reach the early 20s.
It would be warmest for holidaymakers in Queenstown and Wanaka, with temperatures expected to reach 26C and 27C.
Meanwhile, if you're planning to hit the shops tomorrow, you could be rubbing shoulders with a quarter of the population, according to research undertaken by MasterCard.
The research found half of Kiwis thought the rush in shopping centres on Boxing Day was stressful and not worth a hassle, but a quarter would go shopping anyway.
MasterCard New Zealand manager Peter Chisnall said there was a growing number who took advantage of the sales and bought their gifts after Christmas.
But many went Boxing Day shopping for themselves, rather than for others.
Last year, a record $151.7 million was spent across the country on Boxing Day - an 11.2 per cent increase on spending the year before.
Outlook for the week
On Tuesday, a front would move up the South Island bringing a period of rain to the West Coast, Flynn said.
The front would reach the North Island late on Tuesday, bringing patchy drizzle. It would move across the island on Wednesday bringing a period of light rain and drizzle in the west.
Another frontal system was approaching from the southwest of the country later in the week, which could bring some rain on New Year's Eve.
Flynn said the movement of the front would indicate the west and south of the South Island would be most likely to get rain.
MetService would release more details about New Year's Eve later in the week.
BOXING DAY OUTLOOK
Whangarei: Fine apart from morning and evening cloud. Southwest. High 24C.
Auckland: Fine apart from morning and evening cloud. Southwest. High 21C.
Tauranga: Mainly fine with a chance afternoon shower. Light winds. High 21C.
Hamilton: Fine with morning and evening cloud. Southwest breezes. High 22C.
Wellington: Fine with morning cloud. Northerlies developing. High 19C.
Christchurch: Cloud clearing in the afternoon then fine. Northeast developing. High 20C.
Dunedin: Fine with some morning cloud. Northeasterlies developing. High 19C.
- Source: MetService