Temperatures reached 43 degrees Celsius in parts of Victoria on Monday, with firefighters battling about 100 mostly small fires across the state.
The highest temperatures were recorded on the southwest coast, at Warrnambool and Port Fairy.
The continuing heatwave is also affecting South Australia, which peaked at 46 degrees at Ceduna in the far southwest on Sunday.
People in both states have been warned about heat-related illnesses and not to leave children in vehicles.
However a change on Monday night is expected to lower temperatures slightly.