Heat alerts are possible as temperatures rise across the country, with Ashburton expected to hit 31C.
MetService meteorologist John Law said Wednesday would start off warm with a muggy night and continue to heat up in most places as the day progressed.
"Do keep an eye on yourself, make sure you stay hydrated, watch out for your friends and family and do seek shade in the heat of the day as well."
Some wet weather could be expected to head towards Fiordland through to Stewart Island, Law said.
"Some heavy falls of rain are not out of the question in through Fiordland, but you can see most of the wet weather being kept way down across the southern parts of the country and for many of us, it's a dry and fine day and a hot one as well.
"That's really the most amount of rainfall we'll find on these charts over the next day or two. For many of us, it's a dry looking story beneath that high pressure still lingering across the top of North Island."
Law said the eastern side of both the North Island and South Island would really catch the heat.
The east coast of the North Island could reach 29C, while Christchurch could hit 30C and Ashburton, 31C.
Auckland was expected to hit 25C and Hamilton, 27C.
Law said Wellington was not likely to get into the 2s but it was a "fine looking day".
Looking ahead to Christmas Day, MetService's extended forecast was looking dreary for many places.
Auckland was expected to be partly cloudy with rain developing and northerlies while Kaitaia's forecast showed rain, turning to showers and northerlies.
Wellington was predicted to have rain with strong northwesterlies, and Christchurch was expected to have showers, clearing to some cloud and light winds.
Queenstown was expected to be fine with southwesterlies, and Dunedin was the same.
MetService meteorologist Lewis Ferris this week confirmed rain could spoil some people's Christmas plans - but there was still time for a reprieve.
"We might not just see rain on the west coast of the South Island, it might even be spreading up into the North Island, but the typical hot spots, the eastern parts of the South Island, and the North Island, up in the Bay of Plenty, do look like the most likely places to have settled weather next Monday, but we are still a wee way out."
Ferris said certainty of the weather would become clearer as the week went on.
He suggested people wait a few more days before planning to hold their Christmas Day celebrations indoors or outdoors.
RNZ
