A woman walks past charred trees at the Woodford residential area after a bushfire in Blue Mountains on November 12, 2019.

Australian officials warned soaring heat and high winds are already exceeding forecast "catastrophic" conditions on Tuesday as millions of people across the country's east coast braced for the worst bushfires in at least a decade.

Several new fires broke out early on Tuesday, adding to scores of blazes that have been burning for several days across New South Wales (NSW) state.

Three of the 70 blazes were given an "emergency warning level", which means that people are in urgent danger and need to take immediate action.

For people facing two of those fires, officials warned it was too late for them to flee and urged them to find shelter.

"We are certainly starting to see an increase in fire activity," New South Wales Rural Fire Service Commissioner Shane Fitzsimmons, who is providing two-hourly updates on conditions throughout the day, told reporters in Sydney.

"The reality is conditions will simply continue to get worse and deteriorate in the coming hours and particularly into this afternoon."

Bushfires are a common and deadly threat in Australia's hot, dry summers, but the ferocity and early arrival of this year's outbreak has caught many by surprise. Blazes have been spurred by extremely dry conditions after three years of drought in parts of NSW and Queensland, which many experts attribute to climate change.

Sydney, home to five million people, was among several regions rated at "catastrophic fire danger" for Tuesday, the first time it has received that designation since new fire danger ratings were introduced in 2009 following the country's most deadly fire on record.

Residents of the harbor city, which is ringed by large, dry areas of bushland, woke up to a smoky haze on Tuesday.

Lawmakers and firefighters in NSW, said they were prepared, but warned there was only so much they could do. The worst of the weather was not expected until later in the afternoon and through the evening, with temperatures forecast to

reach 37 degrees Celsius (98.6 degrees Fahrenheit), along with winds up to 70 kilometers (43 miles) per hour.

"It's a bit of the calm before the storm at the moment," Prime Minister Scott Morrison told 2GB radio. "Nature will throw some curveballs today, no doubt."