"It's obviously found in the areas where the sun's not hitting the road and anywhere surrounded by forestry."
He said drivers should look out for shadows across the road, especially on corners.
"When you're driving in icy conditions give yourself plenty of space when you are following someone else so you have enough time to stop safely.
"Reduce your speed prior to corners and gently accelerate out of corners, not hard planting the foot."
There had been 11 deaths in the long weekend's road toll for New Zealand as of Monday evening.
Another single vehicle crash happened on State Highway 38 near Kaingaroa Forest yesterday.
The driver was taken to Rotorua Hospital with minor injuries and a Rotorua Hospital duty manager told the Rotorua Daily Post yesterday the person was in a stable condition.
MetService meteorologist Emma Blades said Rotorua only got above zero degrees at 10am yesterday. She said the forecast for today was sitting at a low of 2 degrees.
"But that means it could be dropping to below freezing so there could be ice around again, but on Tuesday night the temperatures are picking up and there will be a bit of cloud cover to trap in some of the days heat."
She said on Wednesday it would be cloudy again with showers and then Thursday and Friday looked wet with the temperature picking up again.
"It looks like Rotorua will be moving from the danger of ice to possible surface flooding."
To check for road warnings and closures people should go to www.nzta.govt.nz/traffic.
Staying safe:
- Reduce speed before corners
- Accelerate slowly
- Give yourself plenty of room to stop safely
- Watch out for shadows
- Drive to the conditions
- Plan your trip with plenty of time