"We are expecting conditions to ease in the Sydney areas and down south overnight, and the fire danger will move to the north-west of the state tomorrow," Rural Fire Service commissioner Rob Rogers said.
"We're not quite out of it yet."
All areas in Sydney's North West will be under a total fire ban on Thursday.
Homeowners in Wallacia prepared to defend their homes as bushfires closed in this morning.
Crews blocked off Silverdale Road as waterbombing aircraft came to the rescue, containing the fire.
Sydney has never recorded two days of 34 degrees or more in a row in September.
Records dating back to 1859 in fact show that before this week, Sydney had only reached 34 degrees in September three times, according to Weatherzone's Ben Domensino.
A total fire ban was in place for Greater Sydney, the Hunter, and the Upper Central West regions today and national parks around the Sydney region were also closed.
Temperatures are set to drop after today, with a forecast maximum of 22 degrees for Sydney on Thursday, followed by a top of 19 degrees on Friday.