South Australia braces for Christmas Day bushfire risk

South Australia is bracing for bushfires over the festive season, with authorities predicting the most dangerous Christmas Day fire conditions in decades.

The mercury is set to reach 37C in Adelaide on Friday, with strong northerly winds forecast throughout the morning.

A significant change is tipped to arrive mid-afternoon, bringing cooler temperatures but also very gusty southerly winds and possible lightning storms.

Total fire bans are expected to be issued in up to 10 districts and firefighters will be on standby across the state to deal with any flare-ups.

Country Fire Service state coordinator Leigh Miller says the forecast conditions are the worst he can recall for Christmas Day in almost 30 years.

"We don't need to have catastrophic conditions for bad fires to start," he told reporters.

"We've had many fires continue, throughout all the years we've been in the CFS, in conditions much less than what we're going to be facing on Christmas Day."

Bureau of Meteorology acting regional director John Nairn said Friday's forecast cool change should not be cause for complacency.

"What we're likely to see is that the most dangerous fire conditions are after the change comes through," he said.

Adelaide's temperature is set to reach 38C on Christmas Eve, with total fire bans declared in the west coast, lower south east and eastern Eyre Peninsula districts.