The weather bureau has issued Australia's first "catastrophic" bushfire danger rating for two parts of northern South Australia tomorrow.

The Country Fire Service (CFS) says any fires in the North West Pastoral and Flinders districts will be uncontrollable and there is a very high likelihood that people in their path will die.

The weather bureau says there will be a combination of extremely high temperatures, strong winds and low humidity in the two districts.

It is the first time the rating has been used in Australia since a new national warning system was introduced after Victoria's deadly Black Saturday bushfires in February.

CFS strategic services manager Mick Ayre says residents of the North West Pastoral and Flinders districts must decide whether they will stay or go as soon as possible.

"The best advice we can give you is to think very carefully about whether you can withstand or fight a fire on a day of catastrophic fire ratings," he said.

"If you're not comfortable and if you don't have the equipment and if your property is not prepared, it's better to go and do something else like to go the beach or the shopping centre than it is to take the risk of defending your property or escaping at the last minute."

Mr Ayre says if people decide to leave, they must be gone by early tomorrow morning at the latest.

"In a catastrophic fire danger situation, no houses are definitely guaranteed to survive," he said.

"If you decide to stay you could die in the attempt to save your property... we always reckon it's better for people to be safe than sorry."

Wendy Shirley of the CFS Volunteers Association estimates that about two-thirds of those in bushfire-prone areas have not heard warnings or do not think it affects them.

"It's those two thirds of people that are not only putting their own, their families' lives and their neighbours' lives at risk, but also the lives of our volunteer firefighters," she said.

Eleven schools and preschools in the two districts will need to close tomorrow as a result of the catastrophic rating.

They include Melrose Primary, where principal Ruth Robertson says parents and teachers are in unchartered waters.

"We're all learning... the biggest problem might be if we're not able to contact some families and we're relying on phone contact, which means people have either got to be home or have a mobile with them," she said.

Meanwhile, the CFS says a fire at Craigmore in Adelaide's north has been contained.

The fire off Yorketown Road was travelling north towards Uley Road, Chapman Drive and Walters Road.

It was posing a risk to public safety and residents were advised to activate their bushfire survival plans.

Arson alert

Police patrols will monitor the movement of known firebugs in high-risk fire areas across South Australia in coming days.

Commissioner Mal Hyde says Operation Nomad is an important preventative measure.

"You can never be certain when you prevent a problem from occurring that you have in fact prevented that, but last summer we put this into effect on quite a number of occasions and we did get through the summer OK," he said.

"Whilst it's no guarantee that we will avoid firebugs lighting fires on these days, it's the best we can do at this stage."