The Country Fire Authority said the combination of strong winds and searing temperatures are expected to return and drive flames toward towns east of Melbourne.
The renewed threat came as Britain's Princess Anne visited the blackened townships north of the Victorian capital that bore the brunt of the firestorms that claimed at least 209 lives.
Authorities set up an evacuation centre at Lilydale, 40km from the heart of Melbourne, ahead of a wind change forecast for later today.
More than 150 residents were sheltering in the centre and many more are believed to have left their homes to stay with relatives.
More than 3,500 firefighters are trying to control four major fires still raging in the south-eastern state.
Officials say many of those who died in the wildfires that swept the region over the weekend of 7 February were trapped in their homes or perished in the mad rush to flee.
At Enoch Point, 80km east of Melbourne, the Country Fire Authority warned residents to evacuate immediately if they did not want to defend their homes.
More than a dozen communities in the area were on high alert, and the CFA warned they may not receive any notification if conditions change unexpectedly in the volatile conditions.
A total fire ban was imposed across the state as meteorologists predicted temperatures would hit around 35C with northerly wind gusts of 35km an hour.
