The NSW Rural Fire Service says its crews are working to control a bushfire near houses on Duffie Drive and Melbourne Street, at Aberdare, and Ellalong Street at Kearsley.
There were fears that homes in the area were at risk from the flames, but the RFS says the situation has improved.
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"The immediate threat to properties has eased," it said in a statement. "However people in the area should remain vigilant and follow the advice of firefighters."
People living nearby have been urged to follow their bushfire survival plans, either by preparing to defend their property, or to take shelter.
Containment lines
"We have got numerous fire trucks in that area, and they believe they should be able to hold it," said an RFS spokesman. "Then we can start looking at getting a containment on it."
The temperature at Cessnock was 38.7 degrees Celsius at 6pm (AEDT) on Friday, but was expected to slowly drop overnight.
No residents have been forced to evacuate their homes due to the blaze, but some people chose to relocate from Ellalong Street, the RFS said.
Elsewhere. lightning strikes have sparked three bushfires on South Australia's Fleurieau Peninsula, south of Adelaide.
And several fire zones across the south east of the country remain on catastrophic fire alert amid heatwave conditions.
The hottest spot in New South Wales on Friday was Ivanhoe, while in parts of Sydney, the mercury hit 41.
