Influencing Greymouth's hottest temperature on record is a strong-to-severe marine heatwave, NIWA says. Photo: RNZ / Tracy Neal
Parts of the South Island are seeing record high temperatures, while North Island braces for the impacts of Cyclone Hale.
NIWA forecaster Chris Brandolino told Morning Report Greymouth Airport on Sunday recorded a maximum temperature of 30.9C - the hottest in 76 years of record-keeping.
"It'll be another very warm day today for the South Island, in particular the interior parts, so Southland interior, Otago, the aforementioned West Coast region."
NIWA forecaster Chris Brandolino's full interview on the weather forecast
This was the first time the temperature eclipsed 30C in the town, NIWA said, with the previous record 29.8C from February 2022.
Influencing Greymouth's hottest temperature on record was a strong-to-severe marine heatwave and hot easterly winds, due to La Niña, NIWA said.
"With La Niña, we tend to get more northeasterly or easterly winds, and for places, like Gisborne, Hawke's Bay, Coromandel, Upper North Island, they're exposed to those east to northeast winds," Brandolino said.
La Niña brought the potential for humidity and big rainfall events for those regions, but for the South Island it was a different story, he said.
"Maybe you've heard of the Foehn wind, which is why Canterbury and eastern Otago, the eastern South Island, can get so hot when they get those west to northwest winds.
"Well, this is coming from the east to northeast but opposite, so places like Te Anau, and Cromwell, and Fiordland and Greymouth, they get the real warm weather ... the spikes and unusually warm temperatures, and dry weather too."
Sea surface temperatures near the West Coast are 3-4C above average, NIWA said.
Marine heatwaves had become more frequent and that frequency would continue to grow, NIWA said.