Melbourne has set a heatwave record with four days in a row above 41C, as a cool change moving through the state brings welcome relief.
The city's place in the record books was cemented about 1pm (AEDT) on Friday for the most number of consecutive days where temperatures soared past 41 degrees.
The hot spell placed unprecedented demand on Ambulance Victoria, which attended more than 400 cases of heat exhaustion since Tuesday.
And the state government says the prospect of forced power outages to manage the system during its peak cannot be ruled out.
The Melbourne temperature was just shy of its forecast 44 degrees, recording 43.9C, on par with Thursday.
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The temperature is the highest Melbourne has reached since Black Saturday.
But an afternoon change began moving through Geelong mid-afternoon, dropping the temperature there from 45 degrees to 33.
The change hit Melbourne from about 4.30pm (AEDT), followed by another change in the evening, making for a more comfortable night.
Bureau of Meteorology senior forecaster Rod Dickson says the changes will force the temperature to fall to the low 20s.
"We're expecting a minimum of 19 degrees in the city and about 16 or 17 for most suburbs," he said.
Saturday's forecast of 23 in Melbourne will bring welcome relief but the state's north will have to wait longer for the heat to subside.
By 4pm on Friday, paramedics had treated 55 people for cardiac arrests that day alone, with reports tipped to rise while temperatures remain high.
Eight children were also reported as being locked in cars on Friday, placing their lives at risk, Ambulance Victoria operations manager Paul Holman said.
Extreme heat and bushfires across the state again strained power supplies with demand exceeding 10,000 megawatts on Friday for the fourth consecutive day.
Energy Minister Nicholas Kotsiras says the full return to service of a Loy Yang generator helped improve electricity supply to the state but the prospect of forced power outages could not be ruled out.
Localised power outages may also be sparked by bushfires and lightning strikes.
Power system operator, the Australian Energy Market Operator (AEMO), is monitoring the situation as some fires are burning near major transmission lines.
Health Minister David Davis said Ambulance Victoria has dealt with the most urgent heat-related cases in a timely way.
