More than 20 uncontained fires are raging across NSW as thousands of firefighters remain on standby in the face of some of the worst fire conditions in the state's history.
As the mercury began its steady climb on Tuesday morning, there were 100 fires burning in NSW.
Twenty-one of these fires were uncontained, said NSW Rural Fire Service Commissioner Shane Fitzsimmons.
"Fortunately none of these fires are posing any immediate threat," he said.
"But clearly, under today's conditions, we are concerned with those and we will be monitoring them very carefully."
More than 1500 firefighters worked overnight to control the blazes.
There it a total fire ban on the entire state on Tuesday with temperatures in the state's far west predicted to hit 45 degrees, while in Sydney the mercury is forecast to climb to 43 degrees - making it the third highest temperature on record.
People living in Shoalhaven, the Illawarra and the southern ranges face the most risk.
"We are shaping up for one of the worst fire danger days on record," Comm Fitzsimmons said on Tuesday morning.
"You don't get conditions worse than this, we are at the catastrophic level and clearly in those areas leaving early is your safest option."
Overnight more than a million people were called by telephone or by SMS to reinforce the leave early message.
Com Fitzsimmons said all precautions had been taken.
"Literally, thousand and thousands of firefighters will be on standby today, the aircraft availability will be up around 100 and they will all be at the ready to deal with any new outbreak of fire," he said.
Salvation Army director of emergency services Norm Archer said the organisation had mobilised its resources overnight and had 87 teams on standby across the state.
"The next few days are looking ominous," he said in a statement.
"Many communities may need support should fires occur and we are poised and ready to provide assistance if the need should arise."
Mr Archer urged people in fire danger areas to follow the directions provided by authorities about protection from hot weather and getting out early.
"The Salvation Army would ask people to pay particular attention to their elderly relatives who are living alone and those suffering sickness at this time," he said.
"It's important regular contact be maintained as we move through this difficult period."
Mr Archer said children were also at risk.
"Don't just assume people are OK, check on them and make contact," he added.
It was 30.8 degrees at Albion Park at 6.30am (AEDT) and 30.9 at Nowra, on the south coast.
By 8am it was 31 degrees at Liverpool and almost 27 degrees at the airport and Terrey Hills.
Westerly winds of up to 40km/h are also forecast.
In an update shortly after 8am (AEDT), Comm Fitzsimmons said the entire state was likely to experience very high or above fire danger conditions.
"It is shaping up to be one of the worst fire danger days on record in NSW," he told the Seven Network.
"We can expect the most extreme of fire behaviour should we see a fire develop and take hold...
"It is shaping up to be a very hot and very long day."
Comm Fitzsimmons again urged people in the areas most at risk to get out now.
"Unless someone's got that crystal ball that can tell us where and when that fire is going to start, we certainly don't know, the reality is that under those sorts of conditions, if a fire starts and takes hold it will burn extremely aggressively... and we will not be able to contain it."