The Waitaki Valley township of Omarama temperature was -7.8°C yesterday morning.
MetService said that made it the coldest place in the country, but it did hit a high of 5°C at 3pm.
It was forecasting -3°C temperatures overnight and another "high" of 5°C for the high country settlement today.
MetService meteorologist Lewis Ferris said New Zealand remained under a high pressure system.
Light winds and clear skies combined with long nights meant temperatures in some places were among the coldest seen so far this winter, Mr Ferris said and RNZ reported.