Power company Jemena will ask 1500 customers across Aberfeldie, Airport West, Craigieburn, Essendon, Yarraville and surrounding areas to reduce their electricity consumption between 4pm and 6pm on Friday in a bid to help ease pressure on the grid. It's extremely hot and unusually hot ... this is not a regular summer. Bureau of Meteorology's Andrew Tupper Customers can get as much as $100 in power bill credits if they hit reduction targets. AusNet says 1046 households are on standby ready to reduce their consumption between 5pm and 9pm. The households are mostly in Melbourne’s outer northern and south-eastern suburbs. Authorities are already calling on emergency reserves to avoid blackouts when the extreme heat hits.

A unit at AGL's Loy Yang A coal-fired plant in Gippsland has been offline for months while repairs have been carried out. The unit was supposed to be operating again on Friday to help shore up power reserves in time for the super hot day, but that has been delayed. AGL's group operations executive general manager Doug Jackson said teams were working "around the clock in tough conditions to bring the unit back as soon as possible". A spokesman for the Australian Energy Market Operator said it was closely monitoring the weather, but they did not anticipate any supply shortfalls. "At this stage we can confirm there is adequate electricity supply reserves forecast to meet anticipated demand in all regions," he said.

Soaring temperatures on Wednesday fuelled 40 fires across the state, with the most serious in Gippsland where more than 50,000 hectares have already been burnt since four large fires began on November 21. Loading Temperatures in the north-west of the state are forecast to reach 47 degrees, which would break the existing statewide December record of 46.6 degrees, set at Robinvale in 1976. "It's extremely hot and unusually hot," the Bureau of Meteorology's Andrew Tupper said. "The reason we talk about records is not because we like records - I certainly don't get out of bed in the morning hoping we get maximum temperature records - the reason we talk about records is to highlight this is not a regular summer." Mr Tupper said the cool change would not reach Melbourne until about 10pm or 11pm on Friday.

He also warned the change would bring rainless thunderstorms, which increased the risk of bushfire-causing dry lightning strikes. Route 30 trams have been cancelled for Friday and buses will replace trams on routes 78 and 82, while route 12 trams will be diverted down La Trobe Street. Ambulance Victoria has received a spike in heat-related emergency calls and has already been called to 16 reports of children locked in cars since Wednesday. None of the children have required treatment. Moonee Valley Racing Club has abandoned its Friday night meeting because of the forecast. Emergency Services commissioner Andrew Crisp urged people to check that family and neigbours, particularly the elderly, were coping with the heat.