A bushfire south of Sevenhill in the Clare Valley could escape control lines as temperatures soar into the 40s in the next few days, the Country Fire Service says.

The fire has burnt more than 25 hectares of scrub in steep terrain south of the town and is continuing to burn inside control lines.

A CFS spokeswoman says there is a serious risk that embers will spread beyond that area.

A public meeting will be held in the town's Madonna Hall at 7:30pm to update residents about the fire.

Regional commander John Hutchins says the cause is still being investigated.

"We have over 80 firefighters on the fire ground at the moment. We're putting all the resources we can into this fire today and tomorrow ahead of a fairly gusty wind change on Friday," he said,