Even by the standards of 2019, with an Australian public increasingly conditioned to the threat of unprecedented bushfires and warnings of record-breaking heat, this has been a week unlike those before it.

On Friday, firefighters were battling more than 200 fires across five states as a heatwave engulfing the country pushed temperatures in the south into the mid-40s, and Sydney and other centres were enveloped in a smoke that health professionals warned had been at hazardous levels for nearly a month. Strong winds pushed the smoke 900km south, where it also blanketed Melbourne.

The human cost was emphasised with the death of two firefighting volunteers, both young fathers, who were killed when their truck rolled as they helped defend villages south-west of Sydney. It brought the confirmed fire season death toll to eight. More than 800 homes and buildings have been destroyed in New South Wales alone.

The escalating crisis moved the prime minister, Scott Morrison, to apologise and promise to return early from a Hawaiian family holiday as he faced rising criticism for being absent during a disaster without informing the public he was taking leave. Morrison’s office had earlier denied to journalists that he was in Hawaii.

Until Tuesday, Australia’s hottest day on record had been in January 2013, when the average maximum temperature across the continent was 40.3C. By Thursday, that mark had been beaten three days straight. The new record of 41.9C (107.4F), set on Wednesday, was a full 1.6C hotter than the old benchmark.

Conditions were expected to worsen on Saturday in New South Wales, the site of the majority of the fires, as it was hit by the centre of a mass of hot air rolling across the continent. Authorities warned, with several areas including suburban Sydney facing catastrophic fire conditions of expected temperatures up to 47C, the hottest all year, and gusting inland winds approaching 40kmh, people should not assume firefighters could save them.

The extraordinary heatwave has been partly driven by natural factors – the strongest Indian Ocean dipole event on record that has dragged moisture away from the continent, and atmospheric warming above Antarctica, which heated up the areas worst affected by fire along the east coast – but scientists say it cannot be divorced from the more than 1C rise in average temperatures due to increased atmospheric greenhouse gases.

According to Sarah Perkins-Kirkpatrick, from the University of New South Wales’ climate change research centre, “everything about this is unprecedented”. She says it is hard, after years researching and speaking to the media about the link between emissions and extreme heat, to find the right words to describe what the country is now experiencing.

“Climate scientists have been banging on about it longer than I’ve been alive,” Perkins-Kirkpatrick says. “We all knew at some point that everything would come together in a perfect storm to make people fully realise climate change is here and now it is. We aren’t surprised, but we are equally shocked and saddened.”

The helmets of volunteer firefighters Andrew O’Dwyer and Geoffrey Keaton at a memorial at the Horsley Park Rural Fire Brigade. They were in a truck convoy near the town of Buxton when a tree fell into their path, prompting the vehicle to roll off the road, with both men dying at the scene. Photograph: Bianca de Marchi/AAP

The worsening conditions have come as the Morrison government is feeling heightening pressure at home and abroad for failing to acknowledge and address the climate crisis.

Morrison’s reputation on climate change was forged in early 2017, when he brandished a piece of coal in parliament at the opposition Labor party, telling them, and the public, it was not something that should invoke fear.

As the bushfire crisis worsened over the past month, the prime minister dismissed suggestions that anything Australia did could limit the impact of global heating on the fire threat and refused to meet with former emergency services chiefs who wanted to discuss the climate crisis. It prompted accusations he was failing to show leadership on a national disaster.

The issue came to a head before Morrison headed overseas when, with Sydney shrouded in smoke and its famous harbour near invisible, he called a press conference to discuss legislation to enshrine religious institutions’ right to discriminate against staff, with the bushfires only belatedly raised in the questions that followed.

The ensuing criticism led to a statement two days later in which Morrison acknowledged the bushfires were an emergency and said he accepted the link between climate change and an extended fire season. He rejected criticism of his climate stance at the UN summit in Madrid, where Australia was repeatedly named as one of a handful of countries blocking more ambitious action, as baseless. Then he went overseas.

What was not considered a significant news story, on the basis a prime minister is entitled to a holiday and the issue is the government’s policies, gained momentum as anger over his absence grew on social media. It culminated in a protest outside his Sydney residence, Kirribilli House, on Thursday.

The abrupt cancellation of Morrison’s holiday on Friday came after a picture was posted to Instagram showing the prime minister posing in Hawaii with other Australian tourists, who claimed to have shared a “few bevvies” with him.

In a written statement, he said he had brought forward his leave with his family as he would be travelling overseas on official business next month, but would now come home before his wife and daughters. In a subsequent interview on 2GB radio in Sydney, Morrison said he accepted his absence had “understandably caused a lot of anxiety”. He deeply regretted it.

David Littleproud, the emergency management minister, later said Morrison might have “retrospectively” not gone had he known how bad the bushfire crisis would be.

Critics said the crisis was already well known. In a special climate statement released amid this week’s heatwave, the Bureau of Meteorology said that as early as September most of the east of the continent was “primed for high fire danger ratings”. The three months of spring were the driest and second warmest on record.

At last count, the bushfires had destroyed at least 3.1m hectares in NSW and Queensland alone, an area larger than Belgium. In the process they had razed areas that do not usually burn, including rainforests, wet eucalypt forests and dried-out swamps, and are believed to have coupled with the atmosphere to create giant thunderstorm clouds.

The weather bureau says warmer and drier conditions are expected to continue into the new year. With the onset of the usual northern monsoon delayed, tropical rains are not expected until late January or into February.