Two water bombing aircraft have been added to New South Wales' firefighting arsenal, as the state's official bushfire season begins.

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An Air Crane helicopter named Gypsy Lady and a DC 10 Air Tanker called Southern Belle will be used to drop tens of thousands of litres of water or fire retardant on bush and grass fires.

NSW Emergency Services Minister David Elliott said the additional aircraft would provide assistance to firefighters on the ground.

"When you consider the normal bucket-load carried by a water bombing helicopter is around 1,500 litres and an Air Crane [has] up to a 9,000-litre dropping capacity, the potential impact of these impressive firefighting planes is incredible," he said.

"These two new aviation assets are going to provide reassurance to the communities across the state that they will have [as] safe a summer as possible."

However, Mr Elliott warned communities not expect to rely solely on fire crews.

He urged residents to satisfy their own fire safety responsibilities and prepare a fire emergency plan.

Authorities are warning that it could be a difficult fire season ahead, with a fierce El Nino weather pattern predicted.

Bureau of Meteorology climatologist Agata Imielska said El Nino increased the likelihood of bushfires.

"During El Nino spring and summers we see dry conditions and also warmer temperatures," she said.

"So with these drier conditions and warmer temperatures drying the soil out we really see that bushfire potential increase."

Rural Fire Service Commissioner Shane Fitzsimmons said the aircraft were a great firefighting asset, but people should not be lulled into a false sense of security.

"The season's upon us, the summer's around the corner. It's going to be hot," he said.

"It's going to be interesting to see how hot and dry the winds are out of the centre of the country and how that effects fire weather conditions this season.

"But it's a salient reminder preparation is critical."