Parts of the South Island can expect sizzling spring temperatures as warm air from Australia drifts towards New Zealand.
The unseasonably warm air is tracking across the Tasman Sea from Australia and heading towards the South Island.
The air flow may bring near-record warm temperatures to parts of the South Island interior on Thursday and Friday as a large area of high pressure to the northwest of New Zealand drives warm air across the Tasman Sea.
Maximum temperatures could be 15° Celcius above average in inland Otago, Southland and Canterbury. Temperatures will be well into the 20s.
Niwa forecaster Ben Noll told Morning Report inland parts of the South Island would be hottest.
"We're talking interior portions, so Central Otago, Queenstown-Lakes, interior Southland, perhaps Invercargill but further inland and also interior southern Canterbury on Thursday and Friday.
"We're looking at temperatures well into the 20s and perhaps, perhaps, the first 30°C reading in New Zealand since April. If that were to occur, possibly a place like Alexandra in Otago.
"You get some pretty warm readings, again perhaps 10 to 15°C above the October average in these places.
"[There's] the Australian component and there's also this big area of high pressure over the Tasman Sea and that's helping to cause a west to northwest flow of air and that is a warm direction."
The balmy temperatures probably would not last until Labour Weekend, he said.
"Unfortunately that area of high pressure ... is actually going to fizzle pretty quickly.
"Saturday in the South Island not looking so sharp as Thursday or Friday and then that front that's on the South Island on Saturday could impact the North Island on Sunday.
"The best place for Labour Weekend is probably going to be the east of the North Island."
Above average temperatures were also expected in the upper South Island on Friday.
A front moves up the South Island on Friday, moving on to the North Island on Saturday night or Sunday and increasing the risk for cloud and rain, Mr Noll said.
On Monday, the chance for rain is greatest over the West Coast.