Snow in Lake Tekapo this week. Photo: Supplied / Pete Whalan
Temperatures dropped well into the negatives overnight Friday, particularly inland of the South Island.
MetService recorded lows of -6C in Twizel, St Arnaud and Clyde, and -5C in Ranfurly and Alexandra.
The lowest temperature on Friday was -8.9C in Mount Cook, MetService said.
It was predicting more frosty mornings over the weekend, and rain for the north of the country today.
A yellow heavy rain watch was in place for Northland through til 6pm Sunday.
"Northland, and potentially Auckland and the Coromandel, can expect strengthening winds and some wet weather for the next few days, so keep an eye out for severe weather information," said MetService meteorologist Alwyn Bakker.
"Elsewhere, the building ridge will bring clear skies and frosty starts. Temperatures are set to drop, with much of the country forecast to be colder than usual overnight.
"Nearly all of the South Island main centres can expect freezing nights, with only Dunedin and Westport remaining above zero for the next few days."
While it was a bit warmer in the North Island, most locations south of Auckland would see low single digits overnight.