Orange recorded its hottest December day on record on Friday, and it'll be a mark that'll stand for just 24 hours with Saturday's maximum top temperature expected to eclipse Friday's best with ease.

The mercury kissed 36.4 degrees Celcius twice on Friday, the first time at 1.20pm and then again at 3.30pm.

Orange broke through the 30-degree barrier at 10.50am and stayed well above that mark for the bulk of the day.

And that heatwave will worsen on Saturday.

With smoke haze again forecast for Orange as well, the mercury is predicted to peak at 39 degrees on Saturday afternoon, with record temperatures to be felt across the state.

A mass of hot air sweeping over NSW on Saturday will push temperatures above 40 degrees in many areas, with some places likely to exceed 45 degrees.

This heat won't just be confined to the far west of NSW either, with Bourke and Penrith - some eight hours and over 700 kiloemtres apart - both forecast to reach around the 46 to 47 degree mark.

"The reason we talk about records is not because we like records ... it is to highlight that this is not a regular summer," Andrew Tupper from the Bureau of Meteorology said.

"This is unusually hot, and that's why we need to pay attention to the unusually hot conditions."

Until this year, the hottest temperature recorded in Orange was 34.7 degrees back in 2009.

That mark was bettered on December 10 this year when the heat crept above 35 and was then trumped again on Friday, before another expected record-breaking scorcher on Saturday.

It comes on the back of a record maximum low temperature on December 2, when Orange topped out at what would now be a welcome 10.6 degrees Celcius.

Dubbo is forecast to reach 46 degrees while Bathurst is tipped to top 41.