These bone-chillingly cold mornings look set to continue until the weekend, with temperatures expected to stay below zero.
Weatherwatch.co.nz's Philip Duncan says the country was sitting under a large system of high pressure coming over from the west.
While it will linger for a few days, a "sharp" cold snap will bring rougher weather and sub-zero temperatures in a wider portion over the inner portion of the North Island, bringing more frosts.
Kiwis woke up to a thick frost both underfoot and coated over their vehicles, with some even struggling to open their doors.
St Arnaud in Nelson Lakes was -6C this morning and Waiouru was the coldest place in the North Island with -4.5C. Mt Cook village only got to -5.3C.