South Australians and Victorians face the worst bushfire conditions so far this summer with strong winds and temperatures to soar above 40C in many locations.
Catastrophic fire danger warnings have been issued for Friday for South Australia's Mount Lofty Ranges and in Lower South East region, where residents have been warned to leave their homes by the morning.
"To ensure your survival, you should leave tonight or early tomorrow morning," the SA Country Fire Service warned on Thursday.
"Well-prepared, well-constructed and defended homes may not be safe during a fire."
A fire starting under catastrophic conditions would be extremely difficult to manage and take significant resources and cooler weather to control, the CFS says.
Extreme and severe fire danger ratings and total fire bans have been declared for Friday across all regions except the North East Pastoral area.
In Victoria, total fire bans have been issued for all but the East Gippsland region as northerly winds and temperatures to the high 30s ands low 40s spread across the state.
The worst bushfire conditions are expected in western and central districts, with an extreme fire danger rating in the South West district, where a late, dry wind change has been forecast.
A spokesman for the State Control Centre said the dangerous bushfire weather would continue across Victoria on Saturday. A total fire ban has already been declared for Saturday across the whole state.
"We'll have hot and dry conditions today, and tomorrow will be the worst bushfire conditions we've had so far this summer," the spokesman said.
Strong northerly winds on Saturday will give way to an afternoon cool change that may be dry and may bring lightning strikes.
Extreme bushfire danger ratings will effect the South West, Wimmera, Mallee, North Central and Central regions on Saturday.
Parks around Melbourne, including the Dandenong Ranges National Park, Dandenong Ranges public gardens, the Silvan Reservoir Park, Warrandyte State Park, Plenty Gorge Park and Woodlands Historic Park have been closed for Friday and Saturday.
