Northlander with a water tanker on the fire front in Queensland

Leslie Cullen from Maungaturoto is helping Australian firefighters battle more than 200 fires in Queensland. Photo/Supplied

Northlander Leslie Cullen has joined forces fighting devastating fires tearing through Queensland, working 18-hour days driving his water tanker in the extremes of smoke, heat and flames.

His Bundaberg-based business C and M Water Cartage has lent two tankers to help fight more than 200 fires that have forced thousands to evacuate during the unprecedented six-day emergency.

A "leave now" warning remains in place for Deepwater, while a number of areas including Dalrymple Heights, Winfield, Carmila and Captain Creek are being urged to keep watch.

Cullen is from Maungaturoto and has lived in the Bundaberg suburb of Thabeban— 120km away from where the fires are burning— for about 13 years.

The Advocate managed to speak very briefly to Cullen who said he and others on the ground in Deepwater have been doing 18 hours in the extremes of smoke, heat and flames.

The fires have burnt 19,000 hectares by mid-afternoon on Thursday and authorities urged residents in affected areas to stay on high alert as the threat was still severe.

For the first few days after the fire started, Cullen drove nearly two hours each way to Deepwater, north of Bundaberg, early morning and returned around midnight.

He's now staying in a hotel in the Deepwater area for as long as his services are needed.

His wife Carol said a lot of residents in Deepwater who were directly affected by the wildfires were their water customers who filled up their water tanks during dry spells.

A fire appliance gets filled up from Leslie Cullen's water tanker at one of the sites in Deepwater, Queensland. Photo/Supplied

She said Leslie called the fire authorities on Monday this week to offer help with water supply and later contacted a driver to bring up another truck to Deepwater.

"We know the firefighters here and he had a contact so he rang them with an offer of help and they said 'yes please, come up as soon as you can' and since then we've had two trucks up there.

"He's mostly in a support vehicle because his truck can carry 13,000 litres of water that can keep the fire trucks going for longer."

Carol Leslie said although her husband has helped with suppressing small fires around Bundaberg over the years, the fires in Deepwater and surrounding areas were the largest he had been involved in since moving to Queensland.

"It's getting worse. They've just announced another area, Winfield, where a fire has got hold of and residents are being evacuated. Fire crews can't fight them, they just have to contain them," she said on Thursday.

Carol Leslie doesn't know when he'll be back home, saying he told her on Wednesday he'd be on the fire front "for days".

Leslie Cullen is the older brother of Federated Farmers Northland dairy chairman and Maungaturoto dairy farmer Ashley Cullen.

The dairy farmer and his wife, who played hockey in the Pan Pacific Games on the Gold Coast, spent a week with his Leslie and Carol Cullen after the sporting event finished two weeks ago.

"I was out with Leslie delivering water to that area and the house we went to has turned to ashes, along with several other houses. It's absolutely devastating," Ashley Cullen said.

"It was a fire waiting to happen because people are not allowed to do control burns anymore so the understory builds up and becomes combustible material and makes things worse.

"The temperatures while we were there was getting horrendous and winds were absolutely diabolical," he said.

Fire and Emergency New Zealand has not been formally approached for help.