Heavy rain meant a very wet Boxing Day for the central part of the country, but the clouds are clearing in the lead-up to the new year.

A staggering 15.8mm of rain fell at Wellington airport in the span of an hour today - more than the past 48 days put together, the MetService said.

That caused flash flooding around the capital and a lot of call-outs for emergency services.

Those holidaying in areas including at popular Mt Maunganui found themselves suited up in rain jackets instead of togs.

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Among those fighting the rain at Mt Maunganui Beachside Holiday Park was Tristan Avery, whose tent featured festive tinsel to keep things bright despite the weather.

"We've got a pretty good sturdy tent here and it's nice and dry, so it's not too bad.

"We've got to keep the kids entertained inside and we'll be all good. The tent's been through a hurricane, so I think we should be pretty good.''

But it is out with the old and in with the new, as the last Wednesday of 2017 brings sunshine to much of New Zealand.

Auckland gets a high of 21C and a mainly fine day. Whangarei is mainly fine with a high of 22C, as is New Plymouth.

Wellington gets a reprieve from the rain, with only a few morning showers expected and some cloudy periods.

However, if you are holidaying in Gisborne or the Hawke's Bay, it might be board games for the kids for a little while longer as rain is still forecast in both places.

Gisborne has a high of 18C and an overnight low of 11C. It will be cloudy with showers - some heavy and with hail - and possible thunderstorms until afternoon.

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The Hawke's Bay will get similar conditions - cloudy with showers, some heavy with hail, with the possibility of thunderstorms about the Wairoa district until afternoon.

Further south, it is fine in Blenheim, Christchurch, Queenstown and Dunedin. Temperature highs range from the late teens to 23C.

The MetService said Gisborne and Hawke's Bay could expect showers and southerly winds for a few more days because of a low pressure system just off the East Coast.

"This should clear for New Year's, though,'' a spokesman said.

A ridge of high pressure will spread across the rest of New Zealand, bringing fine conditions leading up to the new year. However, cloudy conditions and rain look likely in the first few days of 2018.

"On New Year's Eve, another trough moves in from the Tasman and there is reasonable uncertainty around this.

"By the change of year, some models have it held back by the ridge, while others have the trough making good ground over New Zealand, spreading rain into western parts.''

The spokesman said much of the trough will move over the country fully by the next week.

"Much of the rain will be in the west, but most places have a reasonable chance of a few millimetres of rain in the first few days of 2018.''