People escape from the heat and sleep on the beach at St Kilda.

People escape from the heat and sleep on the beach at St Kilda. Photo: Angela Wylie

Finally it began arriving. The cool change the entire city had been waiting for began rolling through Melbourne's CBD around 5pm.

The city's temperature peaked at 43.9 degrees at 4pm at the Bureau of Meteorology's La Trobe Street gauge, and by 7.15pm it had fallen to 29.5 degrees.

By around 6am on Saturday morning, the bureau anticipates temperatures below 20 degrees. Other parts of the state remained in heatwave conditions, with Bendigo sitting on 40.5 and Shepparton 41 at 7pm.

The change came after one of the longest heatwaves in the state's history, and the first time Melbourne had experienced four days in a row above 41 degrees since records began.

The week's scorching temperatures took a heavy toll on people across the state with heart problems, with Ambulance Victoria reporting a huge spike in callouts for cardiac arrests.

On Monday, as temperatures rose, ambulances called to cardiac arrests remained at the summer average of a dozen.

But by 4pm on Friday, this had spiked to 55 cases.

Paramedics were also called to eight instances of children being left unattended in cars on Friday - bringing the tally to 57 callouts for this since Monday.

Metro Trains again told its passengers to leave work early and travel outside rush hour where possible, as it struggled to keep the city's trains running well during Melbourne's extreme temperatures.

Scores of trains were delayed or cancelled across the city, frustrating passengers. It followed Metro cancelling 247 out of 2400 trains scheduled to run on Thursday.

There were also sporadic power failures throughout Victoria as the continued extreme heat caused fuses to blow.

Powercor on Friday afternoon reported 447 properties were without power, with most of those occurring across Ballarat, Geelong and a small number in Swan Hill and Horsham.

Parts of Mill Park were left in the dark after a meltdown of an SP AusNet ''power kiosk'', leaving 531 homes and businesses without access to airconditioning.

Just under 1000 households were affected by CitiPower blackouts, including Albert Park and Toorak. A spokesman said most blackouts occurred about 2pm. Jemena also had to reconnect 67 homes in Braybrook.

Several hundred properties in Melbourne's south-east had to wait for power to be restored by United Energy, including Beaumaris, Sandringham and Brighton.

Australian Workers Union Victoria branch director of safety Percy Pillai said people distressed by power failures should consider how workers were coping in the heat as they tried to reconnect electricity.

On Saturday, Melbourne can expect a top of 23 degrees, with a minimum of 19. Sunday is also forecast to reach 23.