By 9:30am, the mercury had already climbed to 39 degrees at Cobar, and was in excess of 35 degrees across a large part of inland New South Wales.

Temperatures will peak in the low to mid 40s this afternoon across most of the inland, placing many November high temperature records on shaky ground.

"Very hot air that has been plaguing central and southern Australia over the last fortnight has finally been dragged eastward in recent days. Fortunately, the extreme coastal fringe will feel the benefit of a sea breeze today, keeping temperatures in the low 30s there," weatherzone.com.au meteorologist Matt Pearce said.

An unwelcome side effect of the extreme heat, very low humidity and strong winds inland is severe fire danger levels. As a result, a Total Fire Ban is in force for most western and southern parts of New South Wales, including the Greater Sydney region. Catastrophic fire danger is forecast for south-western New South Wales this afternoon.

Sydney can expect a top in the city of around 30 degrees this afternoon, but the western suburbs will sweat through a scorching 41 degrees by mid-afternoon.

"Residents of New South Wales, including Sydney, will also notice a fair amount of dust haze around today. This is as a result of the gusty north-westerly winds, which have picked up large amounts of dust from the parched interior. Fortunately, it will not be as thick as the dust storms of a couple of months back," Pearce said.

"The good news is that there is relief in sight. A significant cool change will move through the state on Sunday, dropping temperatures back into the 20s for most areas. Even better is the fact that this change will bring some rain to much of the state, albeit less than 10mm in most locations."