In Oodnadatta, an Outback town in South Australia, the roads melted. Sydney, Australia's biggest city, sweltered through heat of 108 degrees. In Tasmania a Dunkirk-style flotilla of small craft swung into operation to rescue locals and tourists stranded by fires on the isolated Tasman Peninsula.

Australia's summer vacation season has barely begun, yet a heat wave has swept across the country, smashing temperature records and raising questions both about the impact on annual weather patterns of global warming and about Australia's vulnerability to those changes.

Heat is part of the national mythology. It killed some of the country's first white explorers, and has sparked many devastating fires. The worst, "Black Saturday" in Victoria, killed 173 people four years ago. Thanks to better preparation, firefighting skills and a good dose of luck, fires raging in four states in the latest heat wave have spared humans thus far.

Australia is getting ever hotter, though. The 2013 heat wave has set a new record for the highest national average temperature at 104.5 degrees. So far Leonora, a town in Western Australia, has been the hottest place of all, hitting 120 degrees last Wednesday. That is still below the highest temperature ever recorded in Australia, 123.3 degrees at Oodnadatta 53 years ago.

The authorities are preparing for such temperatures as the new normal. The Bureau of Meteorology added new colors, purple and pink, to its weather map to denote temperatures once considered off the scale: 122 to 125.6 degrees and 125.6 to 129.2 respectively. The bureau says that more "significant records" are likely to be set, with no end to the heat wave in sight.

The heat rolled into Western Australia in late December, then moved east. Cloud-free skies over the central Australian desert intensified the effect, along with weak monsoon rains farther north. This produced what the bureau's Alasdair Hainsworth calls an "incredible buildup of heat."

Winds from the north drove the heat into southeastern Australia, where most of the population lives. At least 20 places, including Hobart, Tasmania's capital, have set new heat records since Dec. 30.

Some climate experts are convinced that the 2013 heat wave will prove a turning point in how Australians respond to warnings about human-induced climate change. In a country that relies on fossil fuels for much of its well-being -- coal is the nation's second-biggest export and produces about four-fifths of its electricity -- climate-change skeptics often have swayed political debate.

When she visited areas devastated by fire in Tasmania, Prime Minister Julia Gillard avoided blaming global warming directly, but said that climate change would eventually bring "more extreme weather events."

The Bureau of Meteorology's Aaron Coutts-Smith is less equivocal about the prospects: He says that all six of the nation's states have, in the past decade, recorded a "predominance" of new record temperatures.