The Northland Police Serious Crash Unit was kept busy on Saturday with two crashes in three hours.
The first crash happened about 9.40am near the intersection of Mangatoa Rd and State Highway 12, west of Kaikohe.
Senior Sergeant Brian Swann said two cars and eight people - five of them children - were involved in the crash.
The Northland Rescue Helicopter flew one child in a critical condition to Starship Hospital in Auckland, while the Auckland Westpac Rescue Helicopter flew the other child, who was in a serious condition, to Whangārei Hospital.
Swann said the other people involved in the crash were transported to Bay of Islands Hospital with various injuries.
The crash scene was cordoned off while emergency services attended.
The second crash happened at Okaihau around 12.30pm.
Emergency services were called to the scene of the single vehicle crash near the intersection of Puketi Rd and State Highway 1.
An Auckland Rescue Helicopter Trust (ARHT) spokesman said the male patient in his 20s was taken to Whangārei Hospital in a serious condition.
"He has now been assessed as being in a moderate condition," an ARHT spokesman said.
A police spokeswoman said a passing truck driver who witnessed the crash called 111.
"The car is off the road and the person is lying beside it," police told the Herald.
The man was the only person involved in the crash.
Swann said their had been "lots" of minor crashes on Saturday, which he said were mostly due to driver inattention and failing to drive to the conditions.
While there was not an exceptional amount of rain, the road was wetter than it had been in recent months.