Records have already been broken but the worst of the heatwave sweeping across NSW is yet to come.
Nine places in total broke temperature records on Wednesday - including six all-time records, according to the Bureau of Meteorology.
Whitecliff, in the state's northwest, recorded the highest maximum temperature in NSW of 48.2C just before 3.30pm - an all-time high for the area.
Far-western towns of Wilcannia, Menindee and Ivanhoe are all tipped to reach 48C on Thursday, as the high-intensity heatwave continues.
Total fire bans are in place across much of central NSW, stretching from the Victorian border up to Queensland.
Temperatures in Sydney's west are expected to climb above 40C on Thursday, and as high as 45C by Friday, ahead of an expected cool change on Saturday.
Authorities are again warning people to take extra care in the heat by staying indoors, keeping hydrated and limiting physical activity, during the extreme heat.
Paramedics had to treat numerous patients for heat-related illnesses on Wednesday, including three children in the city's southwest who were suffering from exhaustion, heatstroke and vomiting.
One was taken to Liverpool Hospital in a stable condition.
Sydney rail commuters are being warned there could be delays across the network as temperatures rise.
Air-conditioned trains scheduled for routine checks have been returned to service, while extra maintenance and medical staff are on stand-by.
