Mr Robinson said the crash happened at speed. Two men in the ute suffered minor injuries, while a woman, the only occupant of the car, had to be taken to hospital in the Westpac Rescue Helicopter. She was in a stable condition.
"We had to use the jaws of life to cut the side of the car to get her out," Mr Robinson said.
The woman was trapped for about 20 to 25 minutes. She was initially helped by ambulance staff before she was extracted, which took about five minutes.
"With the serious injuries we have got to make sure they are stable before we start cutting things up."
The busy day started further along the same road about 5.30am when a vehicle struck a power pole.
Two men in the vehicle were not hurt and escaped the scene, although police later caught up with them, Mr Robinson said.
"That pulled the power pole out of the ground."
A police spokeswoman said a nearby resident called emergency services when they heard a bang and then the power went out. It had since been restored.
Everyone involved in the crashes was wearing seat belts.
Mr Robinson said it had been a busy 10 days for the Carterton Volunteer Fire Brigade, which was called to three car crashes last weekend and two during the week as well as those today.
Also this afternoon, northeast of Whanganui, emergency services were called to rural Papaiti Rd where a vehicle was found in a ditch. None of its occupants remained at the scene.
The earlier crashes happened before the big wet hit the bottom of the North Island.
Wellington is being lashed with heavy rain and in wet and dark conditions, a motorist drove into a central Wellington building about 4.20pm.
A police spokesman said at 4.40 the driver was "very shaken" and paramedics were on their way.
The car had been pulled out of the Taranaki St building by the Fire Service.
