Firefighters are warning NSW residents to brace themselves for heatwave conditions that are forecast to fan the more than 100 bushfires raging across the state.
The NSW Rural Fire Service issued a state-wide total fire ban for Wednesday to Saturday due to hot and dry conditions.
"There are difficult and dangerous fire conditions forecast over coming days," the RFS tweeted.
Some 115 are currently burning across the state with 59 of them uncontained.
The huge Gospers Mountain blaze northwest of Sydney was the only fire at "watch and act" alert level on Tuesday afternoon.
Daytime temperatures in NSW and the ACT are expected to exceed 40C from Tuesday through to Saturday while in the western half of the state the mercury is set to top 45C.
The heatwave will likely spark an elevated fire risk across NSW, the Bureau of Meteorology and NSW Health have warned.
"With the heat comes fires so we're expecting some particularly tricky days for the fire response on Thursday, Friday, Saturday and Sunday," BOM acting NSW manager Jane Golding told reporters on Tuesday.
NSW Rural Fire Service Deputy Commissioner Rob Rogers says firefighters will not be able to contain every blaze before conditions deteriorate.
"While we're very concerned about the Gospers Mountain fire, there are more than 100 fires burning throughout the state," he told reporters.
"Anyone of them could cause problems over ensuing days."
The Gospers Mountain blaze destroyed up to 20 buildings in the upper Blue Mountains on the weekend after firefighters lost control of a backburning operation and the fire jumped containment lines.
It is burning on multiple fronts from the Lithgow area in the west, through the Hawkesbury area and towards the Central Coast in the east. It's so far destroyed more than 400,000 hectares.
Nearby, the Mt Piper Power Station continued to operate on Tuesday afternoon with only essential personnel, an EnergyAustralia spokesman said in a statement to AAP.
"Our priority is keeping our people safe and we are liaising with the NSW Rural Fire Service," he said.
Total fire bans are in place on Tuesday for the northwestern and northern slopes regions where the fire danger rating is "very high".
NSW Health's environmental health director Richard Broome said smoke was expected later in the week as temperatures soared.
"The two issues combined do increase the risk, particularly for people who have existing heart and lung conditions who are more sensitive to smoke," he told reporters in Sydney on Tuesday.
