Plummeting temperatures forecast for tonight could threaten to shut North Island roads again after motorists were delayed by closures this morning.
Both the Desert Road on State Highway One and Rimutaka Hill Road reopened this afternoon following a cold snap which travelled up from the lower South Island bringing snow from Rangipo to Waiouru.
Motorists are being warned there could be more delays tonight because thawing snow on the road could freeze and turn to ice.
"If we still have weather, there is a good chance we'll have frost and ice again," NZTA operations manager Mark Owen.
It is hoped a de-icing agent on the surface could prevent icy build up, but the Transport Agency is advising motorists to take care.
"Look at out website and find out when roads open and close," said Owen.
"Just be aware that out crews are out there 24/7 monitoring and working hard to get the road open as quickly as they can and making it safe for everybody."
The New Zealand Transport Agency has the latest highway conditions.
The wintry blast delivered a short, sharp shock to the bottom of the South Island yesterday causing flight cancellations and grief for farmers.
The snowfall yesterday caused some disruption to schools in the south and farmers took precautions to protect newborn lambs.
While most farmers have not started lambing yet a few are in the middle of it and have had some losses.
To find out the weather forecast for your region, click