Total fire bans in much of SA

Hotter temperatures and stronger winds than expected have increased the risk of fire in South Australia on Tuesday, authorities say.

The Country Fire Service says conditions are now extreme in the Mid North, Murraylands and Yorke Peninsula fire districts.

Conditions are severe in eight other districts and the fire risk is very high in the remaining four districts, with total fire bans in place across much of the state.

No major fire incidents have emerged during the day but CFS State Co-ordinator Yvette Dowling says people should be ready for anything.

"The community as a whole should be prepared for any conditions and have a bushfire survival plan," she said.

Ms Dowling says a cool change that was meant to roll across SA throughout the day is arriving later than expected.

It is now likely to hit metropolitan Adelaide at about 4.30pm before gradually moving north-east with rain expected to follow on Wednesday.

The risk posed by a fire that was burning out of control in the Nullarbor from Monday has been reduced.

Only smouldering embers and smoke remain in the affected stretch between the Nullarbor Road House in SA and Western Australia border.