As sweltering conditions bake most of Australia, a NSW Police Force officer has been been crowned 'ewe beauty' for treating a struggling sheep.

The dehydrated sheep was struggling to walk on an injured leg and had been out in the 40 degree Celsius heat all day when the officer came to the rescue.

"Instead of letting the sheep struggle in the heat, the constable put her in the front seat with him and drove her around to a holding pen," the NSW police said in a statement posted on Facebook.

The senior constable from the remote north-western NSW town of Bourke was conducting a search warrant when he spotted the struggling sheep.

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The animal was given a ride in the air-conditioned police vehicle with a seat belt put on for safety.

Social media users praised the officer, calling him a "hero", "top cop" and a "kind-hearted officer full of love".

"We need more of this gorgeous human behaviour," Lisa van der Zalm wrote on Facebook.

"He’s a hero in my eyes," Diane Leslie said.

Isabel Bella wrote: "Nice to see old fashioned manners in the police force. Beautiful."

Ros Isaac simply wrote: "Ewe beauty!!"

"This is the best day that sheep will ever have. Look at it’s beautiful face. So relaxed," Amanda Bull posted.

Others shared their experiences with sheep.

"My Larry loves going for drives too they used to take him to Sydney in the car till he got too big," wrote Rosalie Hill.

"The police showed them how to harness him in an he used to sit on his bum and smile at everyone who passed him in the car he thinks he is a dog."

Temperatures near 50 degrees Celsius

Parts of NSW have already tipped past 40C, as the state braces for what's set to be the peak of a week-long heatwave.

Ivanhoe and Menindee in the far west are forecast to nudge an extreme 48C.

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Health authorities are urging people to take extra care and keep hydrated during the heat, especially the elderly and children.

Read More Soaring heat turns outback into ghost town

Those with heart conditions are also being warned about the dangers during the heatwave, as dehydration can reduce the amount of blood around the body.

"For people with heart disease and those who are at high risk of a heart attack, these changes can overwhelm the heart and could even result in a heart attack," Heart Foundation NSW chief executive Kerry Doyle said in a statement.

But some relief is on the cards for southern and central NSW, as a cooler change pushes through on Friday night and into Saturday morning.

Total fire bans are in place across much of central NSW, stretching from the Victorian border to Queensland.

The NSW Rural Fire Service is already battling nearly 70 fires across the state.

- with AAP