Drivers heading away for the long holiday weekend are being urged to take extra care, with ice, heavy frosts and freezing fog expected on parts of the central South Island highway network.

The King’s Birthday public holiday falls on Monday 1 June, but the weekend is expected to begin early for many families, with a teacher-only day scheduled for Friday 29 May.

NZ Transport Agency said conditions could be hazardous in parts of the Mackenzie Basin, particularly on State Highways 8 and 80, where widespread frosts are forecast on Friday morning as temperatures drop below zero.

Freezing fog may also affect the area throughout the day.

Forecasters have advised NZTA that Saturday could bring further sub-zero temperatures, widespread frosts and freezing fog to parts of the Mackenzie Basin, creating an elevated risk of ice on roads and bridges.

Rain is expected to arrive in many areas on Sunday.

Further north, morning frosts are also forecast for alpine and foothill routes, including State Highways 7, 73 and 77, through until Sunday.

Drivers travelling through Central Otago and the Southern Lakes are also being warned to watch for frost and ice over the long weekend.

NZTA contractors will monitor highway conditions and may apply grit or other treatments where ice has formed, or where it is likely to develop.

Motorists are being reminded to drive to the conditions, particularly in icy or foggy weather. That includes using headlights, reducing speed, increasing following distances, and avoiding sudden braking or sharp turning movements.