Australia’s most populous state of New South Wales declared a seven-day state of emergency Thursday as oppressive conditions fanned around 100 wildfires.

Around 2,000 firefighters were battling the blazes, half of which remain uncontrolled, with the support of U.S. and Canadian backup teams and personnel from the Australian Defence Force.

The last state of emergency ran for seven days in mid-November amid “catastrophic” fire risk and was the first implemented in New South Wales since 2013. Central Sydney reached a maximum of 39 degrees Celsius (102 Fahrenheit) on Thursday, while outer suburbs scorched at 42 Celsius (108 F).

A statewide total fire ban announced on Tuesday will remain in place until midnight on Saturday.

Around 3 million hectares (7.4 million acres) of land has burnt nationwide during a torrid past few months, with six people killed and more than 800 homes destroyed.

The annual Australian fire season, which peaks during the Southern Hemisphere summer, started early after an unusually warm and dry winter.

New South Wales Premier Gladys Berejiklian said authorities were concerned with the unpredictable conditions.

“With extreme wind conditions, extreme hot temperatures, we have a good idea, a good sense, of where the most concerning areas are, but again when you’ve got those turbulent conditions, embers and spot fires can occur very unpredictably,” she told reporters.

Sydney’s air pollution levels on Thursday ranged from poor to hazardous. During the past month, hazardous smoke has often blanketed Australia’s most populous city and made its iconic skyline barely visible.

Hospitals have recorded a 10% increase in visits from patients with respiratory conditions during the past week.

The Australian Medical Association has recommended people keep hydrated, cool and out of the sun.

Wildfires are also burning in Queensland, South Australia and Western Australia.

The Bureau of Meteorology said Tuesday was the hottest day on record in Australia with an average of 40.9 Celsius (105.6 F) nationwide.

Perth, the capital on the west coast, is experiencing its hottest December with average temperatures for the month at 36 Celsius (97 F) and seven degrees above the mean.

Adelaide, in the southeast, is currently experiencing a four-day heatwave culminating in a sizzling 45 Celsius (113 F) on Thursday.

The unprecedented conditions has reignited debate on whether Australia’s conservative government has taken enough action on climate change. Australia is the world’s largest exporter of coal and liquefied natural gas.

Protesters on Thursday camped outside Prime Minister Scott Morrison’s Sydney residence demanding urgent action on climate change.

Morrison, who is currently on holidays, conceded last week that “climate change along with many other factors” contributed to the wildfires.