A total fire ban is in effect across the greater Hunter as the Bureau of Meteorology bumps up its prediction of Friday's maximums to the mid-thirties in Newcastle and Lake Macquarie.
Singleton is set to reach 37 degrees.
The NSW Rural Fire Service has announced total fire bans in four regions: the state's north west, the Hunter, far south coast and central ranges.
The fire danger rating is "very high" along the eastern side of the state, its north west and the southern Riverina area.
During total fire bans no fires may be lit in the open, and all fire permits are suspended.
Newcastle, Wallsend, Toronto, Maitland and Scone are all predicted to reach 35 degrees on Friday.
Cessnock is expected to get to 36, while Singleton is set to reach 37.
Unlike previous nights this week, temperatures overnight on Friday are not expected to provide much relief with minimums set to stay above 19 degrees in most areas.
Bureau of Meteorology Senior Forecaster Mohammed Nabi said a front moving into the Hunter on Friday was responsible for the latest surge in hot weather.
Maximums are only expected to drop by one or two degrees on Saturday.
Mr Nabi said a cool change should arrive on Saturday evening as the front passes through the region.
"On Saturday night things will start to get cool in a hurry," he said. "Sunday's sunrise temperature will be in the mid-teens."
NSW Rural Fire Service Inspector Ben Shepherd told the Newcastle Herald Saturday is expected to be bring increased fire danger as wind speeds increase to up to 50 kilometres per hour.
"I would encourage residents to check fire danger ratings each day this week of the area they live in and where they are travelling to," he said.
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