Temperatures about the Hunter rose into the mid-30s Thursday while forecasters and the state's Rural Fire Service braced against the possibility of bushfire in inland regions, as a summer hangover lingers through the week.
The mercury hit 37 degrees in Muswellbrook Thursday afternoon - just four degrees shy of the March record - and lingered between 33 and 36 degrees elsewhere in the Hunter and threatening to continue warming toward the weekend.
A cold front following a ridge of high pressure moving across western corners of the state Thursday was expected to bring windier conditions to southeast, and consequently an elevated fire danger, to the southeast, while at home clearing cloud and the chance of morning fog will burn off to clear and balmy days through Sunday.
The Bureau of Meteorology issued extreme fire warnings for the Southern and Central Ranges, with much of the rest of the state considered a high fire risk.
"This is fairly transient weather at this time of the year," BOM senior meteorologist Olenka Duma said.
"We start to see cold fronts making their way further northwards in the autumn.
"With those cold fronts we often see warmer temperatures, which are still occurring in northern and central parts of Australia, dragged across NSW."
The Bureau placed a watch order on its El Nino outlook Tuesday as the prevailing La Nina cycle, which has brought cooler, wetter conditions through much of the summer just gone, continues to wane. The watch means the probability of a transition to El Nino, and the typically warmer and drier conditions its associated with, has reached 50 per cent.
Wetter conditions from three consecutive La Ninas have contributed to more grass growth and vegetation, potential fuel for bushfires, forecasters have warned.
With warmer than average temperatures and drier conditions expected to stretch into winter, the fire risk will linger later than usual.
Total fire bans are in place for the Central and Southern Ranges, Southern Slopes and Lower Central West Plains.
Temperatures reached 35 degrees in Newcastle Thursday afternoon, with possible tops of 38 degrees on Sunday.
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