An extreme heat warning has been issued for southeast Australia, with temperatures set to reach as high as 45degC in the coming days.
Ambulance Victoria state health commander Paul Holman told 9 News there is an "extreme" risk to human health, and fire crews are on high alert.
For parts of the Victorian state, including Melbourne and Geelong, it will be the hottest day since January 2016, reaching a high of 42degC.
Bendigo, Echuca and Avalon are set to reach 43degC, and Mildura and Warracknbeal could reach 45degC.
The Bureau of Meteorology warns mercury will peak on Sunday.
A state-wide fire ban is in place, and people have been told to stay inside.
On Friday the heat was enough to melt the tar on a stretch of the Hume Highway in Broadford, central Victoria rendering it undriveable. Officials warn this could happen again.
Wind speeds are also set to reach 40km/h, creating "blast furnace" conditions, Mr Holman told 9 News.
Fire crews are on high alert and warning residents to prepare for evacuations in the case of bush fires.