Power has been restored to thousands of homes across Melbourne and Victoria following scorching temperatures that resulted in a blackout.

At least 12,000 homes predominantly in the city’s south-east suburbs, including Frankston, Dandenong and Springvale, had been blacked out as a result of sweltering temperatures, United Energy advised on their website just after 9pm.

Ausnet said at least 8000 of its customers are without power, while CitiPower said 1457 properties were in the dark across their network.

Thousands of homes are also powerless in regional parts of Victoria, with the state's west and Mornington Peninsula among the hardest hit.

Numerous energy companies, including Jemena and Ausnet , have said power is not expected to be restored until later tonight.

It comes as the city grappled with temperatures of 38C this afternoon – the mercury was just a little over 37C at 7pm.

The city's train services have also been slowed by the heat. (Twitter via Metro Trains)

Temperatures were even higher in the south-west, with Avalon hitting 42C just after 4pm.

Metro Trains earlier told commuters some services, including those on the Frankston line, had been delayed as a result of the heat.

The Bureau of Meteorology has advised Melburnians that it will be an “oppressive night” of weather, with temperatures not expected to drop below 29C overnight.

Tomorrow is expected to be another scorching day with a top of 35C.