New Zealanders will have to wrap up warm again tonight as more icy temperatures are forecast.
This morning saw the heaviest frosts of the year and temperatures dropping below freezing in several regions.
MetService meteorologist Emma Blades said it wouldn't be quite as chilly tonight but would still be bitterly cold, particularly in the central and upper North Island.
"It's warming up today but the clear skies mean at night all that heat's going to get lost out in space.
"Particularly the North Island's looking very cold. In the South Island it's not as cold because there is more cloud around today."
Unusually, New Zealand's holiday hot-spot the Coromandel was expected to be the coldest part of the country overnight with -2C and a lot of frost forecast for Whitianga.
Waikato was forecast to be cold and frosty. Hamiltonians are in for morning temperatures of -1degC.
Much of Northland was expected to drop to 3degC or 4degC, and Auckland would drop to 6degC before dawn on Sunday.
The Central Plateau is also in for sub-zero temperatures overnight.
Blades said there would be some cloud cover over the lower North Island so Wellington wasn't expected to drop below 9degC.
In the South Island, overnight temperatures are forecast to be about 3degC in Nelson, and 1degC in Blenheim, Christchurch and Dunedin.
Invercargill can expect a relatively mild low of 5C.
