"By Monday, it's generally a cloudier looking day with spells of rain over the North Island and the east of the South Island, with the chance of some heavier rain returning to the Kaikoura Coast."
Temperatures across the North Island would also be milder.
"Although the weekend is looking cloudier and wetter it will do wonders for our overnight minimums on the North Island," Law said.
"For example, Hamilton sees its minimums change from around minus 2C to 10C this weekend."
For the extra day of the long weekend, the pick of the places to be will be on the South Island, especially in the far south or on the West Coast.
"Westland and Southland should keep hold of some fine weather this weekend, although temperatures in the south are still likely to be just below freezing through the nights."
Road policing national manager Superintendent Steve Greally said the winter weather made it even more important to drive to the conditions.
"At this time of year the weather is unpredictable and it's generally worse than it is better," he said.
"I can't urge people enough to check their speeds and to watch their following distances. You need space and time to react, especially in bad weather."
The NZ Transport Agency's safety and environment director, Harry Wilson, said this would be the last long weekend before winter sets in, prompting many people to head away for the break.
"We don't want anyone's holiday weekend to be marred by an avoidable tragedy, so please do the simple things that can keep us all safe – keep your speed down, buckle everyone up and stay focused on the road."
