With that warmth would come the wet, with rain forecast in western regions on Saturday.
"It's been a pretty dry October so far, and this is going to come with some decent downpours for different regions – both west and north," Noll said.
MetService was similarly forecasting wet weather for western parts of southern and central New Zealand by the end of this week, with northwesterly winds to bring warm temperatures to northern and eastern regions.
Northwest winds were also expected to fan temperatures into the mid-twenties in some eastern areas on Friday - and make conditions even hotter and more humid over the weekend.
"Humid northwesterlies will not only bring warm daytime temperatures to eastern regions by the weekend but also bring relatively high overnight temperatures right across the country," MetService meteorologist Peter Little said.
"The warmth and humidity will make sleeping difficult for some as we head into the weekend, so if you haven't done so already it may to time to swap out the flannelette sheets and ready your summer pyjamas."
Noll said that, in the west and north, the humidity might peak at relative values of 80 to 100 per cent.
He saw the better metric as dew point: that's the temperature at which, if cooled, water vapour from the air would condense onto a surface such as grass.
That required 100 per cent relative humidity and occurred when air temperature equalled the dew point.
We really began feeling clammy when the air was both warm enough to make us sweat, but carried enough water vapour to interfere with the process.
"We could consider that a dew point of 13C would mean moderate humidity, and 19C high humidity," Noll said.
"I think we could expect those North Island areas to easily be in the moderate category as look ahead to Friday through Sunday – and for those in the South Island to perhaps be in it too on Saturday."
WeatherWatch head weather analyst Philip Duncan said high humidity values were certainly being seen in places like Waikato, where relative values weren't expected to fall below 50 per cent over the next 10 days – and frequently move into the 90 per cent range at night.
He noted Sunday's lowest forecast humidity value was 82 per cent.
"Put simply, people will notice the warmer nights for sleeping and the warmer days when outside working, especially after the cooler run some places have had lately."
Noll saw New Zealand as being well into a transition period where warmer weeks began to outnumber the cooler ones - "and as we look ahead, that'll come with some humidity, too."
In the meantime, the short week was beginning with a ridge of high pressure in charge, and average to below-average temperatures.
The high moved onto northern New Zealand on Wednesday, then away to the northeast of the country on Thursday, allowing for the northwest flow to become established over the country.
