Canterbury and Marlborough are again sweltering in hot temperatures today with Christchurch, Ashburton and Timaru about 30C or higher.
By late morning Blenheim was also feeling the heat with the temperature gauge reaching 34.4C.
Rangiora, which holds the New Zealand record for the hottest day, reached 34C today.
Eastern parts of the North Island have also been warming up, and Gisborne was expected to reach a high of 35C this afternoon.
But MetService meteorologist Tahlia Crabtree said the heat would not last.
"We've only got one more day of hot temperatures left, at least for the South Island. It's looking like temperatures will drop quite significantly tonight with a cold front moving up the country later tonight."
By mid-afternoon MetService said Timaru's high of 33.2C had faded sharply as cloud covered the city.
It also pointed out the dramatic change in temperatures that was headed the South Island's way with tomorrow's high in Christchurch under half the 37C the city sweltered under last night.
Yesterday the mercury hit 37.5C at Ashburton Airport, 34.7C at Cooptown on Banks Peninsula and 33.7C in Methven as Canterbury experienced its hottest day of the summer.
Heat welcomed by some farmers
Mt Somers arable farmer David Clark said the hot weather had been amazing.
"For arable farmers a run of hot, norwester weather with high temperatures is great for getting harvesting done, it's just what was needed," Clark said.
"It's almost a reflection of Canterbury of old - hot dry days."
It had been a busy few days but production had been high, he said.
"There will be a lot of happy arable farmers around that's for sure, the hot weather brings the seed down to moisture and allows the crop to run through the combine and separate out."
However, high temperatures and working out in the sun all day made for dangerous working conditions, he said.
"We are just making sure everyone is staying hydrated and having more breaks in the shade when they can, and we've been very conscious of fire.
"Everyone's been very vigilant and fortunately there have been no fires."