Scorching temperatures meant power cuts to more than 200,000 Victorian energy customers with the state government admitting the grid failed.
Temperatures peaked at 42.8C in Melbourne on Friday and reached higher at other centres across the state as blackouts lasting up to two hours were imposed at the request of the Australian Energy Market Operator.
The heat meant generators struggled to cope, with two at Yallourn and one at Loy Yang failing.
By mid-afternoon, the temperature had dropped by 15C in 30 minutes and the AEMO confirmed the cuts had ended.
"AEMO acknowledges the inconvenience and hardship of losing power supply during extreme conditions, and thanks all Victorians for their patience," the agency said in a statement.
Earlier in the day state energy Minister Lily D'Ambrosio said she had been assured by AEMO there was enough power in the grid, but as heat built and demand for power grew, the situation changed.
Victorian Energy Minister Lily D'Ambrosio urges patience as the state grapples with power cuts. Source: AAP
"That came on top of the fact that we'd lost three units of power generation from our coal generators in the Latrobe Valley overnight and into this morning," she told reporters.
The AEMO "did what the market operator's job is", acknowledging a gap of about 250MW and taking action, Ms D'Ambrosio said.
"I understand that any loss of power - however brief - is a worry, and that it's something that we would all rather avoid and not see happen.
"People should be rightly disappointed that the power grid was not up to the task."
Melbourne Airport recorded the city's highest temperature of 46C ahead of the change.
The front could pose another threat, Bureau of Meteorology's Kevin Parkin said.
"We are concerned about thunderstorm activity because it may cause more lightning," he told reporters, pointing to the possibility of fires.
A blaze burning since January 16 near Timbarra in East Gippsland flared up on Friday sparking a renewed emergency warning for residents.
"We saw the smoke column jump from only being a couple of kilometres high to 10km or more high, and we saw that smoke column produce its own lightning," Mr Parkin said.
"This type of event ... is incredibly dangerous."
Melbourne is expecting milder temperatures across the weekend, with a forecast maximum of 25C, while northwest parts of Victoria also in line for some reprieve.
