Campbell said north-westerly wind gusts of 80-100km/h were also possible and there was a moderate risk of thunderstorms.
"Avoid unnecessary travel, drive to the conditions and watch out for surface flooding, slips and fallen trees or branches. Driving conditions may be hazardous at times so please reduce your speed to stay safe.
Campbell also urged motorists to be mindful of contractors who could be out clearing hazards off the road and to drive slowly through work sites.
"We want to see everyone get home safely. Stay safe and stay alert."
He also urged motorists to check intended routes for hazards or disruptions before setting out, using the Waka Kotahi Journey Planner website.