A dramatic cool change has swept through Melbourne after residents sweltered through a two-day heatwave.

The change moved through the city centre just after 2pm and caused a massive temperature drop of 12 degrees in seven minutes, according to the Bureau of Meteorology.

The peak temperature in the city on Friday was 42, but the hottest part of the state was Avalon after it hit 45.6.

The cool change first hit Geelong at 1pm with a drop of 44 to 31.

A dramatic cool change has swept through Melbourne after residents sweltered through a two-day heatwave. Photo: AAP More

More than 145,000 customers were left without power across Victoria as the state sweltered through the extreme heat, putting strain on the electricity system.

The Australian Energy Market Operator confirmed on Friday it had asked electricity distributors to “load shed” through the afternoon.

By mid-afternoon the blackouts by distributors totalled almost 150,000.

“It’s all because, you know, we’re balancing the weather, additional heat is stressing the generators,” AEMO chief executive Audrey Zibelman said.

“We have one generator who has had some problems and they have been really struggling to stay on, but they’re having to reduce to protect the machinery.

“Other generators are also struggling, simply because of the heat. So, it’s all that in combination is what we’re confronted with this afternoon.”

Welcome #VicCoolChange has moved through the CBD #melbourneweather #melbweather #vicweather #melbourne's temperature fell 12°C in 7 min. Relief for northern &eastern parts of #Victoria tonight, but the far NE unfortunately will have to wait until Saturday. https://t.co/NzSOfF0Gvg pic.twitter.com/isSTLWdahm — Bureau of Meteorology, Victoria (@BOM_Vic) January 25, 2019





Earlier on Friday, Victorian Energy Minister Lily D’Ambrosio had been assured by AEMO that there was enough power as temperatures reached beyond 40C across the state.

Overnight minimum temperatures of 29.3C at Rutherglen was the northeastern town’s hottest night ever since records began 100 years ago, Bureau of Meteorology senior forecaster Michael Efron said.

Suburban Essendon also recorded its warmest night in 17 years, at 30C.

On Friday, parts of northern and eastern Victoria will sizzle in the mid-40s, potentially breaking more records.

Melbourne CBD reached 42.3C at 2pm, but had rapidly dropped to 30.8C by 2.09pm.

But the change brings risk of rain, thunderstorms and dusty erratic winds and there is also a risk of dry lightning, which could spark more fires.

A total fire ban is in force statewide on Friday and a blaze has broken out in East Gippsland, with an emergency warning issued for Timbarra about 11am.

Updated #VicCoolChange forecast. It arrived in #Melbourne at 2:04pm & the temp has now dropped to just 26.9°C! Thunderstorms are starting to develop in the spotty convective cloud near and east of the change. https://t.co/R7A74b1hnV #VicWeather #MelbWeather pic.twitter.com/7oTzxyS2PA — Bureau of Meteorology, Victoria (@BOM_Vic) January 25, 2019



