"Several members of the public had also managed to make their way down the bank but it was not until fire services arrived that the woman was actually freed," a police spokeswoman said.
State Highway 5 was closed for about 45 minutes while the woman was freed from the vehicle.
The passenger of the car was rescued and taken by ambulance to Taupo Hospital to be checked out along with the man driving.
A police spokeswoman said the pair had minor injuries and the woman was "very cold".
Mr McGill said you could not see the car from the top of road, as the river was flowing quickly and the vehicle was nestled by the bank.
While there was torrential rain and wild weather in the centre and lower parts of the North Island Hawke's Bay escaped the worst of it.
NIWA climate scientist Nava Fedaeff said there would be northwesterly winds today, which meant it would be a warm but windy day.
"Any rain should remain to the west of the ranges and maybe the odd shower for inland parts of the region."
Ms Fedaeff said even though Hawke's Bay was forecast for windy weather today and chilly and wet weather tomorrow with a front coming through it would not be anything like what the rest of the island had gone through.