SYDNEY — Australia is in the throes of one of its most extreme heat events, having broken a national record for the hottest nationally averaged high temperature on two straight days. The Australian Bureau of Meteorology (BOM) reports preliminary data shows that for Dec. 18, the nationally averaged maximum temperature was 107.4 degrees Fahrenheit (41.9 Celsius).

This beat the old record of 105.6 degrees (40.9 Celsius), which had been set just the day before. Before this heat event, the country’s hottest day was Jan. 7, 2013, which had an average high temperature of 104.5 degrees (40.3 Celsius).

The combination of fires, a severe drought and the two record-hottest days has created a sense that an environmental disaster is taking place in a country that is one of the world’s largest emitters of greenhouse gases based on the size of its population.

“Catastrophic” fire conditions, the most severe category, are forecast Friday in parts of South Australia, as hot weather combines with an expected wind shift that could wreak havoc with firefighting operations.

Typically, all-time national temperature records are broken by fractions of a degree, making this week’s records particularly unusual. In addition, having back-to-back national temperature records is also rare. However, heat waves such as this one are being made more possible, severe and longer-lasting because of human-caused climate change.

It’s possible that Dec. 19 will set another national record, and the country’s highest-recorded temperature at a single location — 123 degrees (50.6 Celsius), set on Jan. 2, 1960, in Oodnadatta — may be within reach.

On Dec. 19, Nullarbor, about 600 miles from west of Adelaide, reached 121.8 degrees (49.9 Celsius), which stands as the fourth-hottest temperature recorded in Australia. And Adelaide, a city of 1.3 million, reached 113.5 degrees (45.3 Celsius) Thursday, its hottest temperature recorded in December. Records in Adelaide date to 1887.

On Thursday, the heat, which started over the weekend along the western reaches of Australia and oozed eastward like a magenta-colored inkstain on weather maps, reached areas of southeastern Australia. These same areas have been affected by some of the massive bush fires that have been burning since early spring.

Emergency warnings were issued for the Gospers Mountain Fire upwind of Sydney, which is being called a “mega-fire” for its size and has proved impossible to contain. Friday morning, the Rural Fire Service of New South Wales confirmed that two volunteer firefighters died while battling Green Wattle Creek Fire near Buxton, in southwestern Sydney, when their vehicle hit a tree and rolled over.

“This is an absolutely devastating event in what has already been an incredibly difficult day and fire season,” the agency said in a statement.

This season, about 1.5 times the size of Connecticut has gone up in smoke, particularly from Victoria to New South Wales and Queensland. Satellite-derived data has shown that the country’s emissions of greenhouse gases have increased markedly for November and December, because of combustion from these blazes.

For a second day, Sydney was covered by a thick layer of smoke from the Gospers Mountain blaze that’s burning in the Blue Mountains nature reserve about 100 miles to the west.

“There is incomprehension at the lack of leadership during this climate crisis,” said the mayor of Blue Mountains, Mark Greenhill. “Yesterday in the northern part of the Blue Mountains, I walked through a scenery of devastation and loss.”

A seven-day emergency was declared in the state of New South Wales. The declaration gives the fire service authority over other government departments and the ability to seize property, evacuate people and turn off electricity, gas and oil supplies.

Because of concerns about smoke pollution, some businesses and government departments have stopped operating outside. Many office workers stayed indoors to avoid the searing heat and smoke, which turned the sun into an eerie orange globe dull enough to stare straight at Thursday.

Municipal-run pools, sporting fields and day-care centers in parts of Sydney shut down. Bush fire smoke can worsen asthma and other respiratory conditions, aggravate heart problems and pose risks for the young and elderly alike.

Worried about the possibility of heat-induced deaths, government social workers checked on people experiencing homelessness and handed out bottles of water. Trains were forced to travel more slowly because tracks had buckled in the heat.

In the southern city of Melbourne, a weekly horse racing carnival scheduled for Friday was canceled because the temperature is forecast to hit 109 degrees.

The decision of Prime Minister Scott Morrison to take a one-week family vacation to an undisclosed destination — speculation about his whereabouts was trending Thursday on Twitter — has added to the feeling among many Australians that their center-right government isn’t doing enough to combat global warming.

Police forcibly broke up a small climate protest that had blocked a road outside Morrison’s official Sydney residence. A young girl, in tears, was threatened with arrest.

Supporters of the Liberal-National coalition government say bush fires are common, and there have been far worse droughts. But the intense heat and fires have contributed to the belief among many in the country, which is a big producer of coal, oil and natural gas, that climate change poses a fundamental threat to their way of life.

A national survey conducted by the Scanlon Foundation, a think tank, in July and August, well before the hot weather hit, found the environment was the second-most pressing issue among Australians, behind only the economy, and concern had almost doubled in one year.

According to a new BOM report on the 2019 bush fires, spring brought the highest fire weather danger on record in Australia, as measured by the Forest Fire Danger Index, with “record high values observed in areas of all States and Territories.”

Long-term climate trends in Australia show clear warming and an increase in extreme heat events. Last summer, for example, was the country’s hottest on record, and the BOM found that climate change exacerbated extreme heat events as well as droughts during the year.

Australia has warmed by just over 1.8 degrees (1 degree Celsius) since 1910, with most of the warming occurring since 1950. The BOM has found an uptick in the frequency of extreme heat events and severity of drought conditions during this period, as well.

Nine of Australia’s top 10 warmest years on record have occurred since 2005, and 2019 is likely to join that list. Globally, 2019 is a virtual lock to be the second-warmest year on record, according to NASA and the National Oceanic and Atmospheric Administration.

Freedman reported from Washington.