Temperatures up to 47 degrees Celsius are forecast in northwest NSW and many parts of the state will swelter with the mercury predicted to rise above 40C today.
The tiny outback town of White Cliffs is likely to be the hottest place in the state at an expected 47C, while Bourke is due for a scorching 46C, Dubbo 43C and western Sydney 42C.
The record for consecutive days above 40C could be broken at Bourke, which in 1892 was set at 22 days.
Meanwhile, it will be much cooler in Sydney city with a forecast maximum of 33C and conditions should ease for the southern half of the state during the weekend, a Bureau of Meteorology forecaster told AAP.
But the heat is set to come back early next week with many areas likely to again experience temperatures in the low to mid 40s.
"It's not over yet," the BOM forecaster warned.