Authorities in Australia are urging communities to evacuate as wildfires burn across the east of the country. The appeal comes as firefighters spent the weekend battling out of control blazes which have already burned almost a million hectares of bushland.
Bushfires burning across New South Wales and Queensland states have already killed three people and destroyed more than 150 homes.
Officials expect adverse heat and wind conditions to peak at unprecedented levels on Tuesday.
Bushfires are a common and deadly threat during Australia's hot, dry summers but the current severe outbreak, well before the summer peak, has caught many by surprise.
"Everybody has to be on alert no matter where you are and everybody has to assume the worst and we cannot allow complacency to creep in," NSW Premier Gladys Berejiklian told reporters in Sydney.
The country's most populous city has been designated at "catastrophic fire danger" for Tuesday when temperatures as high as 37 degrees Celsius are forecast to combine with powerful winds for potentially deadly conditions.
It is the first time Sydney has been rated at that level since new fire danger ratings were introduced in 2009.
Home to more than 5 million people, Sydney is surrounded by large areas of bushland, much of which remains tinder-dry following little rain across the country's east coast in recent months.
"Tomorrow is about protecting life, protecting property and ensuring everybody is safe as possible," Berejiklian said.
Lawmakers said the state of emergency - giving firefighters broad powers to control government resources, force evacuations, close roads and shut down utilities - would remain in place for seven days.
On Monday afternoon, the fire service authorised the use of the Standard Emergency Warning Signal, an alarm and verbal warning that will be played on radio and television stations every hour.