Two out-of-control bushfires threatened lives and homes in Western Australia, with blistering temperatures set to intensify in the coming days.

An emergency warning for the outskirts of Perth, the country's fourth-largest city, was issued after a blaze that has now burned through about 100 hectares began yesterday.

Authorities are concerned about the fire reaching residential areas, as fierce winds strain containment lines.

Emergency services have told residents they are "in danger and need to act immediately to survive. There is a threat to lives and homes".

Perth is forecast to hit 34 degrees Celsius today before increasing to near 40C until Saturday.

"The emergency warning remains in place due to the wind intensity that is impacting the fire ground today, which continues to put pressure on containment lines," the Department of Fire and Emergency Services said.

Meanwhile, a second bushfire in the state's southwest had been "contained but not controlled" by yesterday afternoon, authorities said.

Evacuated residents near the small town of Kirup, about 220 kilometres south of Perth, were cautioned not to return to their properties as conditions could remain "very dangerous".

Western Australia has endured record heat this summer, with Perth recording ten days above 40C. Last month the coastal town of Onslow matched Australia's highest-ever temperature of 50.7C.

A year ago, a devastating bushfire destroyed 86 homes in the city's suburbs and burned through 11,000 hectares.

A 40-year-old man was charged with starting the blaze after police alleged he used a spark-producing angle grinder during a total fire ban.

Western Australia was spared the brunt of the devastating climate change-fuelled wildfires in the summer of 2019-20, which mostly ravaged the country's two most-populous states, New South Wales and Victoria.