Heavy frosts expected tonight could lead to treacherous driving conditions in the morning.
Clear skies over inland and sheltered areas across the country will result in sub-zero temperatures, prompting police to urge motorists to drive to the conditions.
MetService forecaster Mike O'Connor said Waiouru would reach -4C and Queenstown would dip to -5C.
"The skies are really clear and there is a high chance of good frosts tonight.''
Frosts were likely to hit anywhere that was sheltered from the southwesterly winds, he said.