Bushfire threat weakens in WA's south

An out-of-control and unpredictable bushfire in Western Australia's south has been downgraded from an emergency warning to a watch and act alert.

There is no longer an immediate threat but people need to remain vigilant near the Balladonia Roadhouse in the Shire of Dundas, the Department of Fire and Emergency Services warns.

"There is a possible threat to lives and homes as a fire is burning in the area and the conditions are changing," DFES said.

"Homes are not designed or constructed to withstand a fire in today's conditions."

Some roads may be closed and drivers are urged to avoid the area or slow down due to smoke.

"If you are in the vicinity of the Balladonia Roadhouse, you can leave in an easterly direction along Eyre Highway, provided it is safe to do so," DFES warns.

The blaze was first reported on December 20.