Four people have died after a head-on car crash in the Waikato this afternoon.

One man and three women died after the accident happened on State Highway 30, 11km east of Benneydale, around 2pm, police said.

The man and two women were in one car, in which two children also sustained life-threatening injuries.

The other car had two people, one woman who died and a man who was taken to Waikato Hospital.

Bad weather stopped air ambulances from Rotorua and Taupo from flying to the accident.

Ambulance operator St John urged motorists to take extra care when driving in wet and foggy conditions.

Traffic travelling from Mangakino to Benneydale would have to wait until the serious crash unit finished its scene examination, as there were no detours, police said.