Australia’s most populous state was paralysed by “catastrophic” fire conditions on Saturday amid soaring temperatures, while one person died as wildfires ravaged the country’s southeast, officials said.

“Catastrophic fire conditions are as bad as it gets,” New South Wales Rural Fire Services Commissioner Shane Fitzsimmons told reporters. “Given we have a landscape with so much active fire burning, you have a recipe for very serious concern and a very dangerous day.” Areas in western Sydney were forecast to hit 4°C.

Cooler air was expected to move through New South Wales late Saturday, although authorities warned that strong winds could push fires in dangerous new directions.

New South Wales is in a seven-day state of emergency, with around 2,000 firefighters battling 100 wildfires.

Some major roads heading to the south and west from Sydney were closed for part of the day and authorities asked people to delay travel at the start of the Christmas holiday period, warning of the unpredictability of the fires due to high winds and temperatures above 40°C. A cooling but powerful wind with gusts of up to 90kph from the south swept through the state late on Saturday, lowering temperatures significantly but also creating risks that the winds could spread the flames and embers.

“Today has been an awful day,” NSW Rural Fire Services Commissioner Shane Fitzsimmons said of the conditions which were rated “catastrophic”, the highest level of danger.

Fitzsimmons said conditions in Sydney may not have reached forecast catastrophic levels, although they did elsewhere. He said the haze from the fires that has choked the city in recent weeks might have helped cap temperatures on Saturday by acting as insulation.

The devastation has put pressure on Prime Minister Scott Morrison, who has received criticism for going on a family vacation in Hawaii during the wildfire crisis. He apologised on Friday for any offense “caused to any of the many Australians affected by the terrible bushfires by my taking leave with family at this time.” Morrison cut short his vacation and returned home on Saturday night. He is due to visit the New South Wales Rural Fire Service headquarters on Sunday.

Two firefighters died on Thursday battling blazes southwest of Sydney. Geoffrey Keaton, 32, and Andrew O’Dwyer, 36, were in a truck convoy southwest of Sydney when a tree fell and caused their vehicle to roll off the road.

Authorities confirmed on Saturday that one person died and 15 homes were destroyed in South Australia as a wildfire ravaged the Adelaide Hills on Friday, just 40km from the state capital of Adelaide.

Another person was critically injured after fighting to save his home from the fires.

That follows the death of a 24-year-old man in a road crash in South Australia on Friday, which sparked a fire in the area of the Murraylands.

Authorities said 23 firefighters and several police have also suffered injuries, as more than 40,000 hectares burned across South Australia.

“It is going to be a real scene of devastation, especially for those people in the Adelaide Hills who have been most affected,” South Australia Premier Steven Marshall said. “We know that in addition to the buildings and vehicles lost, there are very significant losses in terms of livestock, animals, crops, vineyards.” The annual Australian fire season, which peaks during the Southern Hemisphere summer, started early after an unusually warm and dry winter.

Around 3 million hectares of land has burned nationwide during a torrid past few months, with nine people killed and more than 800 homes destroyed.

Fatih Birol, International Energy Agency executive director, believes Australia has missed opportunities to mitigate the impact of coal.

“I find the Australian energy debate far too emotional, far too nervous and far too hot. It is hotter than the climate change itself,” he told The Sydney Morning Herald and The Age.

Protesters on Thursday camped outside Morrison’s Sydney residence demanding urgent action on climate change. Morrison, who critics have deemed a climate change sceptic, conceded earlier this month that “climate change along with many other factors” has contributed to the wildfires.

Associated Press