The mercury reached 29.5°C between 2pm and 3pm, which not only shattered the previous hottest April day on record, it totally outshone the hottest day of our recent summer.
Niwa National Climate Centre climate scientist Gregor Macara said the 29.5°C recorded at Musselburgh weather station was "quite remarkable" because it was a whole degree hotter than the previous record.
"That’s amazing — very impressive."
The previous April record was 28.5°C, which was recorded on April 4, 2021.
The records began in 1947, and the only other time the mercury neared this level was on April 8, 1955, when it hit 26.6°C.
He said it was also impressive because the temperature was hotter than any of the temperatures recorded during Dunedin’s recent summer.
"That’s classic.
"Dunedin’s highest temperature for summer — from the start of December 2024 until the start of March this year — was 28.6°C, on December 3 and 8.
"It’s nearly a degree different, and it’s highly unusual to have your hottest day in April.
"It was unusual enough that the highest temperatures occurred in December, because we typically have our hottest temperatures in January and February.
"So, to get it in April, that’s exceptional."
Mr Macara said it was also very hot in other parts of the region.
"Alexandra hit 28.3°C, Clyde 27.1°C, Cromwell 27.2°C, Lauder 25.3°C, Queenstown 25°C and Ranfurly was 24.2°C.
"So, it was obviously quite widespread around the region."
He said the sweltering temperatures were caused by strong northerly foehn winds.
"Broadly, we had a very warm northerly flow, and we had wet weather that we saw on the West Coast ... and up into parts of the North Island, which was caused by that so-called atmospheric river.
"It delivered moisture from the subtropics, but equally, it not only delivered moisture, it also delivered heat, and that’s what we saw on the downwind side of the main divide."
Foehn winds occur when an air mass hits the Southern Alps, dries out as it travels over the mountains and then warms up again as it travels down the other side.
"We were left with the sort of dry, warm remnants of that," he said.
Today’s weather is expected to be considerably cooler, with cloudy skies, the chance of an afternoon shower, southwesterlies turning northeasterly and a high of just 16°C.
