A sweltering heatwave has breathed new life into bushfires, with fears heat exhaustion could prove deadly among the community.
The mercury is tipped to reach the high 30s and low 40s across Victoria from Sunday to Tuesday as part of a three-day heatwave.
Temperatures topped 43C in Warracknabeal and Walpeup in the state's west on Sunday afternoon, while Melbourne's peak hit 38C.
There will not be much respite in the evenings, with overnight minimums expected to stay high.
"There's not going to be a lot of opportunity for people's bodies to recover from the heat of the day overnight," State Control Centre spokesman Luke Heagerty said.
"So it's critical that you reassess what your plans are for the next few days and make sure you're taking it easy on your body."
Most at risk are those older than 65, babies and young children, pregnant women, people with acute and chronic health conditions and socially isolated individuals.
Authorities are urging people to plan activities for the coolest part of the day, drink plenty of water, wear light and loose-fitting clothing and check on family, friends and neighbours.
"Extreme heat can be a killer," Premier Jacinta Allan told reporters.
"That's why it's so important that we look after ourselves and look after each other."
Those struggling to stay cool in their homes should head somewhere cool with air conditioning, such as a shopping centre or a friend's place.
The heat is making life difficult for more than 500 firefighters - who have been batting bushfires for much of summer - on the ground in the state's west.
Firefighters were working to set up containment lines and back-burn in preparation for the heatwave but fires in the Little Desert and Grampians national parks made the most of the conditions.
The Little Desert blaze, sparked by dry lightning on January 26, was declared contained but broke away on Sunday afternoon.
The breakout sparked an emergency warning for people to leave the townships of Goroke, Gymbowen and Nurcoung as it raged south.
An emergency warning was issued earlier for the small farming community of Mirranatwa and the Victoria Valley area as the northerly winds picked up in the Grampians.
People were told to flee towards Dunkeld and advised to take refuge at the Hamilton Performing Arts Centre or with family and friends outside the warning area.
Horsham incident control centre operations officer Jarrod Hayes said the fire situation was dynamic and rapidly changing.
"Those outbreaks have been challenging," he said.
"We've had multiple aircraft, including rotary-wing helicopters and fixed-wing firebombers ... working on all three of these fires."
High levels of smoke and ash have been reported in the area, with a smoke haze from the Grampians fire blanketing Adelaide on Sunday morning.
Elsewhere, vast parts of Western Australia faced high and extreme fire danger ratings on Sunday as historic rainfall led to life-threatening flooding in north Queensland.
