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Motorists are being urged to take care on State Highway 1 between Otaki and Levin in Horowhenua, after massive downpours left surface flooding.
Sergeant Noel Bigwood told NZPA the Tararua Ranges behind Otaki had so far today recorded 176.5mm - 14mm more than the previous daily record.
Mr Bigwood said the flooding across the highway had come from the Waitohu Stream that had burst its banks.
"It's causing a lot of disruption and we're advising people not to travel unless they really have to. And if they do, allow plenty of time."
The heavy rain started in the ranges about midnight and was due to ease off tonight.
Te Horo Beach Road was also flooded after the Mangaone Stream overflowed.
Mr Bigwood said the Mangaone Stream had gone from a flow of about three cubic metres a second to nearly 30.
"The Otaki (river) has gone from an absolute minimum flow to up near 800 cubic metres a second and the Waitohu's gone from virtually a dribble up to around 80 cubic metres a second."
Mr Bigwood said there were some tramping groups in the hills in the area, but they were well equipped and experienced groups who would be able to cope with the weather.
"Once it stops raining tonight the rivers will drop pretty rapidly by Thursday."
- NZPA
