Niwa forecaster Ben Noll said subtropical winds from near New Caledonia meant temperatures across the region were likely to be several degrees above average for early September.
''We are forecasting unseasonable warmth on Thursday and Friday across the east of both islands, where temperatures may rise to between 5deg and 10deg above the average maximum daily temperature.''
Coastal areas in Otago could expect temperatures up to 18degC today , and tomorrow could be as warm as 20degC in northern parts of Otago, he said.
A pattern of high pressure passing over the top of the country drawing warmth southward could be repeated several times during the first half of the month.
''As a result, a couple of rounds of record-breaking maximum and minimum temperatures are possible.''
Tomorrow parts of Canterbury could reach highs of 25degC.
The region's warm spell was likely to last until early next week. However, warmer temperatures were likely to bathe the Otago again from September 10, he said.
''Spring will certainly come in style for Otago.''
The forecast weather pattern typically caused dry conditions in the east of the South Island, an area already plagued by below normal rainfall and soil moisture, Mr Noll said.
The warm spring weather follows winter records which made the first eight months of the year New Zealand's warmest on record.
New Dunedin resident Warren Jowett (75) says Dunedin's weather is one of the many reasons for living in the city.
Formerly of Staveley, Ashburton district, Mr Jowett moved to the city at the end of April with his wife Marita (76).
Mr Jowett said they were enjoying living in the city so much he decided to make a list of the city's merits. Four months in, the list had grown to 52 reasons.
Yesterday, Mr Jowett photographed the cherry plum blossom trees in Wycolla Ave, St Clair.
He said he was pleasantly surprised to have found himself listing the city's climate as another point on his list.
''A.H. Reed wrote about the climate here. It sums up the perception that others have of Dunedin's climate perfectly.
''Others think Dunedin's climate is colder than it actually is.
''It's a misconception held by those who live the subtropics.
''But we shouldn't tell too many people how good it is here,'' he said, joking.
His list included ''practical'' things like ''being able to turn on the tap and have good water flowing'', as well as an appreciation for the ''unpretentious, friendly nature of Otago-ites'' and the wealth of cultural activities.
