NSW firies head to WA to battle bushfires

Firefighters from NSW, the ACT and the Northern Territory will join their West Australian counterparts on Saturday as they battle to control bushfires in the state.

WA Premier Colin Barnett says virtually all of the state's firefighters are committed to the Northcliffe fire, where a natural disaster has been declared, and another major blaze at Lower Hotham.

Reinforcements from NSW, the NT and the ACT will arrive on Saturday.

They'll include incident management specialists, aviation specialists and ambulance officers.

Part of the contingent will be 160 rural and inner-city firefighters from NSW.

The wind is forecast to change directions several times over the weekend and temperatures in the southwest of the state may hit 40C.