A total fire ban is in place across the greater Sydney and Hunter region, as well as the North Coast and north-west.
A bushfire warning has been issued in the Hunter Valley for Richmond Vale, with a number of properties under threat.
According to the NSW Rural Fire Service, the fire has broken containment lines, but aircraft and firefighters are working to prevent it spreading further.
There is another blaze at Beacon Hill on Sydney's northern beaches.
It's the first time that Sydney has recorded a 33-degree day this early in spring in 150 years of data.