Authorities are concerned over the record-breaking heatwave in Australia, and it has asked the Aussies to take all the necessary precautions to avoid falling ill due to the rising temperatures.

Prime Minister Julia Gillard on Tuesday reiterated public warnings issued by various concerned agencies as temperatures soared above 40 degrees and firefighters get busy with hundreds of fire cases in the southern states.

Victoria's ambulance service treated 45 patients for heat-related illnesses on Monday, including four cases of children left in cars, the Sydney Morning Herald reported.

Adelaide recorded its hottest New Year's Day since 1900 with 41.6C.

The South Australian power company has also been affected by the searing heat matched with strong winds. On Monday, it cut electricity supplies for several hours to over 3000 properties on the Fleurieu Peninsula, a location of thriving tourism-related businesses. The action was met with criticism from the business owners who claimed there was no notice of the power interruption.

The Herald spoke to paramedic Darren Murphy who said there was a heat-related case reported every five minutes.

"We've gone to patients who are nearly 100 years old, they live at home alone, wearing heavy clothes, they have an air conditioner but they're not using it for whatever reason," Mr. Murphy said as he advised people to stay indoors.

"We've gone to people who are in their mid-30s, who have been working outside all day, were drinking (water) but just not drinking enough and then we've also gone to young children who have either been at the beach or they've been left in their cars for short periods, who have been heat-affected as well."

Diamantina Shire Council tourism and community manager Steve Baldwin said on Tuesday the temperature was nearly 44 degrees Celsius, and it will be even hotter on Wednesday and Thursday.

Mr. Baldwin has advised tourists and motorists to carry extra water and have extra petrol.

He added it is best to stay indoors doing what is safe in extreme temperatures.