Four trapped in car in flood water

Four people are trapped in a car in rising flood water north of Auckland as rain continues to fall in the region.

Fire Service spokesman Jaron Phillips says the water at the scene on Wayby Valley Rd, near Wellsford, was waist deep.

"They can't get out and there's a risk of being swept away," he said.

"Fire crews are there now attempting a rescue."

This creek in Makarau, north of Auckland, turned into a river after heavy rain bombed the area. Photo: Supplied

Emergency services were alerted around 6.30pm.

Earlier on Wednesday, State Highway 16, which had been closed between Kaukapakapa and Wellsford, was open to traffic again.

However, the NZ Transport Agency urged motorists to take extreme caution because of various depths of flooding.

Auckland Civil Defence and Emergency Management said steady rain was continuing north of Orewa and on Great Barrier Island, with a further 30mm-60mm expected over a six-hour period from late afternoon.

The area had already been soaked by 110mm of rain in the previous 24 hours.

Head of operations Aaron Davis said more surface flooding was likely and he encouraged people to avoid driving unless absolutely necessary.

He said road closures were in place and localised slips had occurred, with more slips expected.

"People need to be aware of rapidly rising rivers and streams and the potential for slips, and should not drive through flood waters."

- With NZN