Isolated showers in Northland could ruin New Year's Eve parties but fresh westerlies will keep the humidity at bearable levels.
MetService weather forecaster John Law said since the high east of the Chatham Islands was not likely to budge, Northland and other parts of the country would continue to have warm spells.
"There's still some uncertainty in the timing of troughs in the westerlies crossing New Zealand. So if you're planning outdoor activities for around that time, it will be important to keep up-to-date with the latest MetService forecasts and any watches or warnings."
Weather Watch analyst Richard Green said "rogue showers" would be experienced in Northland and Monday looked to be the best day at this stage.
There would be day highs of 24C and 18C at night, he said.
"But it won't be as sticky and cloudy as we've had so far. Northlanders will have some respite from the recent humidity."
Cloudy periods, with isolated showers, especially in the afternoon and evening, and a northwest breeze are forecast for today.
Northerlies will start developing later tomorrow, with showers towards the evening.
On Sunday, showers will turn to rain during the day, with winds turning fresh westerly. Fine spells and a few showers are predicted for New Year's Eve while a few showers will grace Tuesday.
Dargaville, Kaikohe and Kerikeri will experience showers with westerlies for most of next week, except Wednesday.
Whangarei airport recorded 25.8C on Boxing Day.