The warm weather is set to continue this week with no rain in sight for at least four or five days.
But the fine, settled conditions could come to a dramatic end at the end of the week if the remnants of Cyclone Oma arrives on New Zealand's shores.
Forecasters said it was too early to predict whether the cyclone would track towards New Zealand, but that it was one of several possibilities.
"Tropical cyclones are known for their unpredictable behaviour and things can change extremely rapidly," said MetService duty forecaster Sarah Haddon.
"The models are doing two completely different things with it. One option is that it will move down and affect New Zealand, but there are also options where the high that is around New Zealand blocks us, and it moves towards Australia."
Cyclone Oma, currently near Vanuatu, has been upgraded to Category 3, meaning it has highly destructive winds of more than 160km/h.
Niwa said that if the cyclone did reach New Zealand, it would produce heavy rain, wind and rough seas.
Most parts of the North Island will reach the mid-20s today, and will remain warm and settled until Thursday. There is a very small chance of a showers, Haddon said.
Auckland is likely to reach 25C today, and will get warmer as the week progresses, peaking at around 27C on Thursday.
"It won't be as hot as what we've seen over the last month or so," said Haddon.
The rest of the North Island will have similar temperatures, though it could get warmer in Gisborne and Napier, and Wellington will be slightly cooler.
Today: 25C, cloudy, possible shower before lunch. Southeasterlies.
Tomorrow: 27C, cloudy, possible after shower. Northeast breezes.
Today: 25C, cloudy at time, possible isolated showers north of Waitemata Harbour. Easterlies.
Tomorrow: 25C, cloudy periods, southwest breezes.
Today: 24C, fine then some cloud in the evening. Easterlies turning northerlies.
Tomorrow: 26C, morning cloud then fine. Northwest breezes.
Today: 24C, fine spells, light winds.
Tomorrow: 23C, morning cloud, then fine.
Today: 21C, fine. Northerlies developing this evening.
Tomorrow: 22C, fine. Northeasterlies.
Today: 23, fine, some morning and evening cloud. Northeasterly breezes.
Tomorrow: 26C, mainly fine, some evening cloud.