If Ouyen reaches 49°C as predicted, it would surpass Victoria's all-time temperature record, last set during the devastating Black Saturday bushfires of 2009.
Nearby Mildura is forecast to endure up to six consecutive days above 43°C, well beyond any previous heat streak. Updated forecasts suggest the city could also reach 49°C - two degrees hotter than its historical maximum.
Melbourne is expected to climb to 44°C, its hottest day since Black Saturday, when catastrophic fires claimed 173 lives across the state.
Emergency Management Commissioner Tim Wiebusch described the conditions as "extremely serious," warning Victorians to prepare for prolonged heat and elevated fire risk.
Ambulance Victoria has urged residents to limit outdoor activity, stay hydrated, avoid alcohol and check regularly on vulnerable people, including the elderly, children and those with medical conditions.