Authorities on Friday upgraded the blaze in Nambeelup, about 70km south of Perth in the Peel region.
"You are in danger and need to act immediately to survive. There is a threat to lives and homes," WA's Department of Fire and Emergency Services said.
"If the way is clear, leave now for a safer place."
The fire, which has burnt through 100 hectares since Wednesday, is moving fast in a northeasterly direction and is out of control.
Aerial support has been sent to assist firefighters on the ground.
Residents near the town of Denmark on WA's south coast were earlier urged to flee an out-of-control bushfire that poses a threat to lives.
An emergency warning remains in place for parts of Shadforth, west of Denmark, with affected residents advised to leave immediately if the path is clear or prepare to shelter in their home.
"Houses on Point Hillier Vista, McLeod Road and the east end of Limbourne Road are under threat from fire," the DFES said.
"Residents in the emergency warning area, leave in a southerly direction towards South Coast Highway, and then travel on the Highway east towards Denmark.
"William Bay National Park is closed and people are asked to leave the area."
An evacuation centre has opened at Denmark Recreation Centre.
The blaze is moving slowly but is described as uncontrolled and unpredictable.
An emergency bushfire in Rockingham, south of Perth, was downgraded on Thursday to an "advice" level, with residents advised to monitor conditions.
Train services on the Mandurah line between Rockingham and Cockburn Central were cancelled on Friday morning but have since resumed.
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