Sydney is facing catastrophic fire conditions for the first time since the current fire ratings were introduced in 2009.
Residents in the Greater Sydney, Greater Hunter and Illawarra/Shoalhaven regions are being urged to develop a bushfire survival plan as firefighters prepare for "catastrophic" conditions on Tuesday.
Those living in these regions are being warned that flames will be hard to suppress and homes will not withstand coming into contact with the firefront.
Thirty-five local government areas from Sydney's beachside suburbs including Manly, all the way to the Blue Mountains in the west, could be affected.
Residents in the Hunter including those at Dungog, Lake Macquarie, Singleton, and the Upper Hunter are also being encouraged to take preventative measures.
Authorities have also upgraded the rating to catastrophic for the Illawarra and Shoalhaven areas south of Sydney.
The Rural Fire Service says residents must prepare and review their bushfire survival plan.
Step 1: Discuss
One of the most important things to do before a bushfire is to decide what you’ll do if one should start.
Leaving early is your safest choice.
Alternatively, you can decide to stay - but only if you're well-prepared.
Consider unexpected events such as a resident being home alone, if you aren’t home, if the fire moves faster than expected or if the phone lines and electricity are down.
If you're not sure or aren't prepared to stay, you should leave early.
Step 2: Prepare your home and get ready
A number of simple preventative measures will help you prepare your home for a bushfire, including trimming overhanging trees and shrubs and clearing your gutters of debris and leaves.
Step 3: Know the bush fire alert levels
If there is a fire in your area you will find its alert level on the NSW RFS website, on the radio and on the "Fires Near Me" app. You need to keep track of the alert level so you know what you should do.
Step 4: Keep key information
In a bushfire, it’s important that you stay up-to-date on conditions in your area. The NSW Rural Fire Service strongly advises becoming familiar with the quickest sources of information.
In an emergency, call Triple Zero (000). For information on bushfires, call the Bush Fire Information Line 1800 NSW RFS (1800 679 737)
For bushfire survival information in 12 additional languages, please visit the Rural Fire Service's translated fact sheets.
Bushfire and Natural Hazards CRC Chief Executive Dr Richard Thornton told SBS News it is crucial residents make plans for a worst-case scenario.
"If you're living in those areas that are going to be impacted by the catastrophic warnings...really think seriously about what you're going to do," he said.
"(The trigger for) when you're leaving shouldn't be when the flames are at my front door."
Australia's worst bushfire tragedy was the Black Saturday fires of February 2009, which killed 173 people and destroyed thousands of homes. It would have carried a catastrophic rating under the present system.