The spate of road deaths began early afternoon on Friday at Marsden Point in Northland, when a 31-year-old man and his 13-year-old son were killed when their car collided with a petrol tanker around 12.10pm. The man lost control on a straight section of road in heavy rain, police said.
"The car spun out of control and hit the tanker backwards," said Senior Sergeant Ian Row.
"The tanker driver had slowed down to almost zero because he was only a short distance away from turning right for a local delivery."
An unmarked police car heading to the crash also collided with another vehicle on State Highway 1 about 500m north of the Mangapai intersection. Two police officers and the driver of the other car were injured.
Just before 2pm on Friday, a 34-year-old woman crashed a car into a tree on Tauhei Rd, about 15km north of Morrinsville in the Waikato.
She had to be freed from the car by emergency services and was flown to Waikato Hospital, where she died around midnight on Friday.
Her husband received minor injuries in the crash.
In Christchurch, a car and a motorcycle collided on Queen Elizabeth II Drive, Burwood soon after 9.15pm on Friday.
The motorcyclist died at the scene. The driver of the car received minor injuries.