Melbourne is set to swelter this week, with three days forecast above 40 degrees.
As the first real taste of summer hits, temperatures in parts of rural Victoria will soar to 44 degrees.
The hot spell begins on Monday as the 2014 Australian Open kicks off in Melbourne.
Melbourne is forecast to reach 35 degrees, followed by 41C on Tuesday, 39C on Wednesday, 41C on Thursday, then 40C on Friday.
Other parts of the state are also set to sizzle, with five days in a row to hit above 40 in northern Victoria.
In the towns of Echuca and Swan Hill the mercury is tipped to rise to 44 on Thursday and Friday.
"It's the first burst of proper heat this summer," Bureau of Meteorology senior forecaster Terry Ryan told AAP.
But the heatwave is not likely to set records in Melbourne, which endured three consecutive days of at least 43 degrees in January 2009, the week before Victoria's Black Saturday bushfires.
"They were the hottest three days ever in Melbourne," Mr Ryan said.
The longest hot spell recorded in Melbourne was in 1908, when the temperature hovered above 40 for five consecutive days.
Premier Denis Napthine urged Victorians to stay hydrated, look after their neighbours, particularly the elderly, and be aware of fire risks.
"We are in the height of our fire season," he told reporters in Melbourne.
"I can assure Victorians all fire services are ready to deal with any emergency, but people need to be alert, people need to be conscious of the risk and people need to be prepared to make decisions to leave early and live."
A change is expected to sweep through Melbourne late on Friday, with Saturday's forecast of 26C to provide welcome relief.