Temperatures in Sydney's west are expected to soar above 40 degrees Celsius today, while the city's east should be spared thanks to a sea breeze.
Penrith is forecast to reach 43C today, while the city will only reach 35 degrees.
"Yesterday some very hot air was sitting over inland New South Wales [with] temperatures reaching 43 degrees, now that air is coming over Western Sydney today,"
A total fire ban has been declared for the Greater Sydney and Illawarra-Shoalhaven regions.
The north-west and the central-west [will be] particularly affected with temperatures increasing up into the mid-40s early next week and Tuesday in particular looks to be the hottest for western districts.