Bushfire in SA's southeast not a threat

A bushfire is burning in South Australia's southeast but isn't threatening people or property.

The fire near Bordertown comes as the mercury is set to hit 34 degrees in the southeast and Adelaide and push into the low 40s in some regional centres on Wednesday.

Strong winds will also add to the fire risk.

"If a fire breaks out it may be difficult to contain," Country Fire Service state coordinator Leigh Miller said.

"It is vital the community is on high alert."

The CFS says the fire risk will be either severe or extreme across the state.