Emergency warning for regional WA bushfire

An emergency warning has been issued for an out-of-control bushfire threatening farm properties in Katanning in Western Australia's southeast.

Affected residents must leave immediately if the path is clear or prepare to shelter in their homes, the Department of Fire and Emergency Services says.

About 100 firefighters are battling the blaze, which started near the intersection of Great Southern Highway and Sirl Road just before midday on Friday.

Two bushfires are meanwhile threatening lives and homes in Western Australia's Wheatbelt region.

A watch and act alert has been issued for parts of Lake King, Lake Camm and Varley in the Lake Grace shire.

The blaze started near the intersection of Biddy-Camm Road and Fence Road in Lake King on Thursday afternoon.

Some roads may be closed and drivers are asked to avoid the area and reduce speed due to smoke.

A watch and act alert has also been issued for a bushfire caused by lightning in the nearby town of Hyden.

Fire conditions have intensified due to a wind change, ahead of a possible thunderstorm later on Friday.

About 60 firefighters are on the scene.