Dozens of wildfires are burning out of control. Fire authorities say 68 fires were burning across Victoria yesterday and 16 were blazing across South Australia. One person died of "fire-related" causes in the Grampians, northwest of Melbourne.

The Climate Council, a privately run group of climate scientists and economists who previously formed the government-funded Climate Commission, defines a heatwave to be at least three consecutive days at a temperature in the top 10 per cent for that time of year.

Its interim report states there will still be record cold events but that these events are being eclipsed by record hot events by a ratio of three to one. Heatwave frequency in Australia will "increase significantly", it warns.

"As greenhouse gases continue to accumulate in the atmosphere from the burning of fossil fuels, more heat is trapped in the lower atmosphere," the report says. "This increases the likelihood that hot weather will occur and that heatwaves will become longer and more intense.

"It is crucial that communities, emergency services, health and medical services and other authorities prepare for the increases that are already occurring in the severity and frequency of many types of extreme weather.

"The south-east of Australia, including many of our largest population centres, stands out as being at increased risk from many extreme weather events - including heatwaves."

Dr Sarah Perkins, report co-author and research fellow at the UNSW, said the heatwave was happening during a "neutral" period of climatic variability.

"Before the 2009 Black Saturday fires, there was a decade-long drought, which produced some climatic variability reasons behind it," she said. "This year, we aren't in an El Nino, we're in a neutral pattern, so we might expect some extreme weather but not this.

"I'm not discounting natural variability, but there is still the background signal of climate change. The high-pressure system probably would've happened anyway, but climate change is exacerbating events."