Parts of the South Island are set to swelter later this week, with some areas reaching just shy of 30 degrees Celsius.
It comes as a large area of high pressure moves onto the country from the Tasman Sea before drifting eastward.
Heavy rain may bring some reprieve to the sticky weather, however.
The north of the country is expected to see a sub-tropical low develop, bringing with it humid easterly winds which may bring wet weather to Northland on Friday and possibly over the weekend.
"Computer weather models are all developing a low to the north of New Zealand on Wednesday, then moving it slowly southwards, possibly bringing heavy rain to Northland on Friday," MetService meteorologist Peter Little said.
"The models currently differ as to how far south they spread the sub-tropical moisture and rain associated with this low, so there will probably be some fine-tuning of forecasts for northern New Zealand later in the week as models come to a consensus."
While the weather is expected to be mainly fine for many regions, some showers will be thrown into the mix, with heavier showers possibly on the cards for some inland areas.
A front is expected to bring a brief burst of rain to the south on Friday, preceded by warm northwesterlies in the east of the South Island.
"The front that is forecast to move over southern New Zealand on Friday is expected to weaken rapidly as it moves northwards, so only a few millimetres of rain are likely in most places," Little said.
"The warm northwest winds ahead of the front are expected to push daytime temperatures in the east of the South Island towards 30C, which will be around 10C warmer than the start of the week."
Southland, Otago and Canterbury are expected to take the brunt of the warmer weather.
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