But the eastern heat is expected to pass before Christmas Day, with moderate conditions forecast for all.
MetService's outlook for Christmas Day is for sunny skies and light winds in most places with temperatures in the low to mid-20s.
"However, southerly winds are forecast to bring a few showers into eastern parts of the North Island, and a northeasterly wind is expected to pick up in Christchurch in the afternoon," said meteorologist Dan Corrigan.
Looking ahead to Boxing Day, a front moves on further south, but the forecast remains dry and settled for most of the country.
Niwa forecaster Nava Fedaeff said the effects of tropical storms may be felt here.
While it was a wee bit off to be certain, Niwa would be keeping a close eye on progress, Fedaeff said.
"There might be something brewing there. We are at the time of the year when there are potential for tropical disturbances. We're in tropical cyclone season whether it's actually a cyclone or not, there could be some systems from the north."
Fedaeff said there were also very warm seas, which could boost storms from the north.
