UPDATED 1.22pm: Heavy rain across Northland has caused flooding forcing motorists on State Highway 16 to turn around.

The road is closed in both directions between Kaukapakapa and Wellsford because of heavy flooding near West Coast Road.

A severe weather warning is in place for Auckland, Great Barrier Island and the Coromandel Peninsula.

Philip Duncan from WeatherWatch.co.nz said there's been a huge dump of rain.

"The rainfall rate per hour is above the normal band for rain, we are talking about rainfall numbers that are more typical of a summer downpour, but it's consistent all through the morning - that's what's unusual for this.

MetService has warned another 70mm to 120mm of rain could accumulate on top of what has already fallen.

Fire Service shift manager Carren Larking said crews have rescued one person from a flooded house in Whangaripo Valley Road, Wellsford and three abandoned cars have been found in Waiteitei Road.

"We're expecting quite a bit of rain this afternoon, through til tomorrow morning, so we are planning on being busy."

Thames Coromandel District Council said the Muriwai Stream ford at Port Jackson is impassable and a small slip was blocking one lane on the Whitianga side of The 309 Road.

It's warning residents to tie up boats, check moorings and move stock as roads in the northern Coromandel area risk flooding during high tide.

Reports are now coming in of schools starting to close.

Ahuroa School near Puhoi has been forced to shut because of the floodwaters.

Principal Michelle Nell said the river levels were high when she arrived at school this morning.

"One of our feeder roads was flooded so we decided to close the school, because we wouldn't be able to get all the children home after school."