A bushfire is burning uncontrolled in scrub on Kangaroo Island posing a threat to lives and property.

The Country Fire Service has issued an emergency warning for the fire at Gosse, on the island's southern coast, about 23 kilometres from Parndana.

The CFS says conditions in the area are continually changing and it will soon be too dangerous for people to leave.

A second fire north of Adelaide has already damaged buildings and glasshouses on a property new Two Wells, with both fires sparked amid severe conditions.

A watch and act warning is in place for the Two Wells blaze which is burning in stubble about four kilometres south of the town.

The fire has impacted one property near Horseshoe Crescent but is not expected to cause problems for neighbouring residents.

The fire's progress has been slowed as it continues to burn in grass and plastic materials, producing smoke which could be harmful.

Locals have been urged to activate their bushfire survival plans and, if not prepared to defend their properties, leave the area if it is safe to do so.

The fires came as very hot conditions persisted across much of South Australia on Thursday.

Temperatures climbed into the low 40s in some regional centres with the mercury also hitting 40C in Adelaide.

Total fire bans were imposed in five districts, the west coast, the lower Eyre Peninsula, Yorke Peninsula, Kangaroo Island and across the Mt Lofty Ranges.